Secondary battery with a radical compound active material

ABSTRACT

A radical compound may be used as an active material for an anode layer  2  to provide a novel stable secondary battery with a higher energy density and a larger capacity. The radical compound used has, for example, a spin concentration of 10 21  spins/g or more.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a stable secondary battery with a higherenergy density and to an active material used therein.

2. Description of the Prior Art

As markets for a note-type personal computer and a mobile telephone havebeen rapidly expanded, there have been increased needs to a small andlarge-capacity secondary battery with a higher energy density used inthese devices. To satisfy the needs, a secondary battery has beendeveloped, which utilizes an electrochemical reaction associated withcharge transfer on alkali-metal ions as a charge carrier such as lithiumions. Among others, a lithium-ion secondary battery has been used in avariety of electronic devices as a stable and large-capacity secondarybattery with a higher energy density.

Such a lithium-ion secondary battery uses a transition-metal oxidecontaining lithium in a positive electrode (cathode) and carbon in anegative electrode (anode) as active materials, and performs charge anddischarge utilizing insertion in and elimination from these activematerials.

However, since the lithium-ion secondary battery uses a metal oxide witha large specific gravity particularly in a positive electrode, it has aninsufficient secondary battery capacity per a unit weight. There havebeen, therefore, attempts for developing a large-capacity secondarybattery using a lighter electrode material. For example, U.S. Pat. Nos.4,833,048 and 2,715,778 have disclosed a secondary battery using anorganic compound having a disulfide bond in a positive electrode, whichutilizes, as a principle of a secondary battery, an electrochemicaloxidation-reduction reaction associated with formation and dissociationof a disulfide bond. The secondary battery uses electrode materialscomprising elements having a smaller specific gravity such as sulfur andcarbon as main components. Although these materials are effective tosome degree in providing a large-capacity secondary battery with ahigher energy density, it has a small efficiency in reformation of adissociated bond and exhibits insufficient stability in a charge ordischarge condition.

Furthermore, there has been suggested a secondary battery also utilizingan organic compound, i.e., a secondary battery using a conductivepolymer as an electrode material. It is a secondary battery whoseprinciple is doping and undoping reactions of electrolyte ions on theconductive polymer. The doping reaction as used herein is a reaction ofstabilizing excitons such as charged solitons and polarons generated byoxidation or reduction of a conductive polymer by counter ions. On theother hand, a undoping reaction as used herein refers to a reactionwhich is opposite to the above reaction and in which excitons stabilizedby counter ions are electrochemically oxidized or reduced. U.S. Pat. No.4,442,187 has disclosed a secondary battery using such a conductivepolymer as a positive electrode or negative electrode material. Thesecondary battery is constituted with elements with a lower specificgravity such as carbon and nitrogen, and thus has been expected to bedeveloped as a large-capacity secondary battery. A conductive polymer,however, has a property that excitons generated by oxidation orreduction are delocalized over a wide region of

-electron conjugated system and interacted with each other. It resultsin a limitation to a concentration of excitons generated, and therefore,to a capacity of a secondary battery. Thus, a secondary battery using aconductive polymer as an electrode material is effective to some degreein terms of weight reduction, but is not adequately effective in termsof increase in a capacity.

As described above, there have been various proposals for a secondarybattery which does not use a transition-metal containing activematerial, in an attempt to achieve a large-capacity secondary battery.There have been, however, provided no stable secondary batteries with ahigher energy density and a large capacity.

As described above, in a lithium-ion secondary battery using atransition metal oxide as a positive electrode, a specific gravity ofthe element is so high that it has been theoretically difficult toprepare a secondary battery with a larger capacity than that currentlyused. An objective of this invention is, therefore, to provide a novelstable secondary battery with a higher energy density and a largercapacity.

SUMMARY OF THE INVENTION

To solve the above problems, this invention provides:

-   -   [1] a secondary battery comprising at least a positive        electrode, a negative electrode and an electrolyte, wherein an        active material in at least one of the positive electrode and        the negative electrode contains a radical compound;    -   [2] a secondary battery comprising at least a positive        electrode, a negative electrode and an electrolyte, wherein an        active material in at least one of the positive electrode and        the negative electrode is a radical compound;    -   [3] a secondary battery comprising at least a positive        electrode, a negative electrode and an electrolyte, wherein an        active material in at least one of the positive electrode and        the negative electrode consists of two or more materials, at        least one of which is a radical compound;    -   [4] a secondary battery utilizing an electrode reaction of an        active material, wherein the electrode reaction in at least one        of the positive electrode and the negative electrode is that        where a reactant or product is a radical compound; or    -   [5] a secondary battery utilizing an electrode reaction of an        active material, wherein two or more electrode reactions occur        in at least one of the positive electrode and the negative        electrode and at least one of the reactions is that where a        reactant or product is a radical compound.

In the present invention, a positive electrode means a cathode and anegative electrode means an anode.

In the above secondary battery, the active material may be a positiveelectrode active material.

In the above secondary battery, the electrode reaction may be that inthe positive electrode.

In the above secondary battery, the electrode reaction in the positiveelectrode may be a discharge reaction in which the radical compound is areactant.

In the above secondary battery, the electrode reaction in the positiveelectrode may be a discharge reaction in which the radical compound is aproduct.

In the above secondary battery, the discharge reaction may be thatforming a bond between the radical compound and an electrolyte cation.

In the above secondary battery, the discharge reaction may be thatcleaving a bond between the radical compound and an electrolyte anion.

In the above secondary battery, the electrolyte cation may be a lithiumion.

In the above secondary battery, the radical compound may have a spinconcentration of 10²¹ spins/g or more.

In the above secondary battery, the radical compound may be a neutralradical compound.

In the above secondary battery, the radical compound may be a stableradical compound.

In the above secondary battery, examples of the radical compound includethe followings:

-   -   wherein X₁ and X₂ are a substituent containing at least one of        an aliphatic group, an aromatic group, hydroxy, alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro,        nitroso, halogen or hydrogen, provided that when X₁ and X₂        contain an aliphatic group, the aliphatic group may be saturated        or unsaturated, substituted or unsubstituted, and straight,        cyclic or branched, and may contain at least one of oxygen,        nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms;        when X₁ and X₂ contain an aromatic group, the aromatic group may        be substituted or unsubstituted and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; when X₁ and X₂ contain hydroxy, the hydroxy may        form a salt with a metal atom; when X₁ and X₂ contain alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro or        nitroso, these substituents may be substituted or unsubstituted        and may contain at least one of oxygen, nitrogen, sulfur,        silicone, phosphorous, boron and halogen atoms; X₁ and X₂ may be        the same or different; and X₁ and X₂ taken together may form a        ring;    -   wherein R is alkyl which may be substituted or unsubstituted,        straight, cyclic or branched, and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; X is a substituent containing at least one of an        aliphatic group, an aromatic group, hydroxy, alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro, nitroso, halogen        or hydrogen, provided that when X contains an aliphatic group,        the aliphatic group may be saturated or unsaturated, substituted        or unsubstituted, and straight, cyclic or branched, and may        contain at least one of oxygen, nitrogen, sulfur, silicon,        phosphorous, boron and halogen atoms; when X contains an        aromatic group, the aromatic group may be substituted or        unsubstituted and may contain at least one of oxygen, nitrogen,        sulfur, silicon, phosphorous, boron and halogen atoms; when X        contains hydroxy, the hydroxy may form a salt with a metal atom;        when X contains alkoxy, aldehyde, carboxyl, alkoxycarbonyl,        cyano, amino, nitro or nitroso, the substituent may be        substituted or unsubstituted and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; X may form a ring; and the alkyl R may be        tert-butyl;    -   wherein R₁ and R₂ are alkyl which may be substituted or        unsubstituted, straight, cyclic or branched, and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; R₁ and R₂ may be the same or different;        X₁ and X₂ are a substituent containing at least one of an        aliphatic group, an aromatic group, hydroxy, alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro, nitroso, halogen        or hydrogen, provided that when X₁ and X₂ contain an aliphatic        group, the aliphatic group may be saturated or unsaturated,        substituted or unsubstituted, and straight, cyclic or branched,        and may contain at least one of oxygen, nitrogen, sulfur,        silicon, phosphorous, boron and halogen atoms; when X₁ and X₂        contain an aromatic group, the aromatic group may be substituted        or unsubstituted and may contain at least one of oxygen,        nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms;        when X₁ and X₂ contain hydroxy, the hydroxy may form a salt with        a metal atom; when X₁ and X₂ contain alkoxy, aldehyde, carboxyl,        alkoxycarbonyl, cyano, amino, nitro or nitroso, these        substituents may be substituted or unsubstituted and may contain        at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; X₁ and X₂ may be the same or different;        and X₁ and X₂ may form a ring; and both of the alkyls R₁ and R₂        may be methyl;    -   wherein R₁ to R₄ are alkyl which may be substituted or        unsubstituted, straight, cyclic or branched, and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; R₁ to R₄ may be the same or different;        X₁ and X₂ are a substituent containing at least one of an        aliphatic group, an aromatic group, hydroxy, alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro, nitroso, halogen        or hydrogen, provided that when X₁ and X₂ contain an aliphatic        group, the aliphatic group may be saturated or unsaturated,        substituted or unsubstituted, and straight, cyclic or branched,        and may contain at least one of oxygen, nitrogen, sulfur,        silicon, phosphorous, boron and halogen atoms; when X₁ and X₂        contain an aromatic group, the aromatic group may be substituted        or unsubstituted and may contain at least one of oxygen,        nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms;        when X₁ and X₂ contain hydroxy, the hydroxy may form a salt with        a metal atom; when X₁ and X₂ contain alkoxy, aldehyde, carboxyl,        alkoxycarbonyl, cyano, amino, nitro or nitroso, these        substituents may be substituted or unsubstituted and may contain        at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; X₁ and X₂ may be the same or different;        and X₁ and X₂ may form a ring; and all of the alkyls R₁ to R₄        may be methyl.

The radical compound may be the nitroxyl radical compound represented bygeneral formula (A6) where the nitrogen atom in the nitroxyl radicalgroup is bound to at least one aryl:

-   -   wherein Ar is aryl which may be substituted or unsubstituted and        may contain at least one of oxygen, nitrogen, sulfur, silicon,        phosphorous, boron and halogen atoms; X is a substituent        containing at least one of an aliphatic group, an aromatic        group, hydroxy, alkoxy, aldehyde, carboxyl, alkoxycarbonyl,        cyano, amino, nitro, nitroso, halogen or hydrogen, provided that        when X contains an aliphatic group, the aliphatic group may be        saturated or unsaturated, substituted or unsubstituted, and        straight, cyclic or branched, and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; when X contains an aromatic group, the aromatic        group may be substituted or unsubstituted and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; when X contains hydroxy, the hydroxy        may form a salt with a metal atom; when X contains alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro or        nitroso, the substituent may be substituted or unsubstituted and        may contain at least one of oxygen, nitrogen, sulfur, silicon,        phosphorous, boron and halogen atoms; X may form a ring; and the        aryl may be substituted or unsubstituted phenyl.

The radical compound may be the compound forming substituted orunsubstituted heterocycle, represented by general formula (A7):

-   -   wherein X is carbon, oxygen, nitrogen, sulfur, silicon,        phosphorous or boron atom, provided that X may be the same or        different; X may be bound via saturated or unsaturated bonds; X        may form a bond with any substituent; this compound may be a        polymer which may be straight, cyclic or branched; and n is an        integer of 2 to 10 both inclusive.

The above radical compound may be the nitroxyl radical compound having apiperidinoxyl ring structure, represented by general formula (A8):

-   -   where R₁ to R₄ are alkyl which may be substituted or        unsubstituted, straight, cyclic or branched, and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; X is a substituent containing at least        one of an aliphatic group, an aromatic group, hydroxy, alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro,        nitroso, halogen or hydrogen, provided that when X contains an        aliphatic group, the aliphatic group may be saturated or        unsaturated, substituted or unsubstituted, and straight, cyclic        or branched, and may contain at least one of oxygen, nitrogen,        sulfur, silicon, phosphorous, boron and halogen atoms; when X        contains an aromatic group, the aromatic group may be        substituted or unsubstituted and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; when X contains hydroxy, the hydroxy may form a        salt with a metal atom; when X contains alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro or nitroso, the        substituent may be substituted or unsubstituted and may contain        at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; and X may form a ring.

The above radical compound may be the nitroxyl radical compound having apyrrolidinoxyl ring structure represented by general formula (A9):

-   -   where R₁ to R₄ are alkyl which may be substituted or        unsubstituted, straight, cyclic or branched, and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; X is a substituent containing at least        one of an aliphatic group, an aromatic group, hydroxy, alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro,        nitroso, halogen or hydrogen, provided that when X contains an        aliphatic group, the aliphatic group may be saturated or        unsaturated, substituted or unsubstituted, and straight, cyclic        or branched, and may contain at least one of oxygen, nitrogen,        sulfur, silicon, phosphorous, boron and halogen atoms; when X        contains an aromatic group, the aromatic group may be        substituted or unsubstituted and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; when X contains hydroxy, the hydroxy may form a        salt with a metal atom; when X contains alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro or nitroso, the        substituent may be substituted or unsubstituted and may contain        at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; and X may form a ring.

The above radical compound may be the nitroxyl radical compound having apyrrolinoxyl ring structure represented by general formula (A10):

-   -   where R₁ to R₄ are alkyl which may be substituted or        unsubstituted, straight, cyclic or branched, and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; X is a substituent containing at least        one of an aliphatic group, an aromatic group, hydroxy, alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro,        nitroso, halogen or hydrogen, provided that when X contains an        aliphatic group, the aliphatic group may be saturated or        unsaturated, substituted or unsubstituted, and straight, cyclic        or branched, and may contain at least one of oxygen, nitrogen,        sulfur, silicon, phosphorous, boron and halogen atoms; when X        contains an aromatic group, the aromatic group may be        substituted or unsubstituted and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; when X contains hydroxy, the hydroxy may form a        salt with a metal atom; when X contains alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro or nitroso, the        substituent may be substituted or unsubstituted and may contain        at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; and X may form a ring.

The above radical compound may be the nitronylnitroxide compoundrepresented by general formula (A11):

-   -   where X₁ to X₃ are a substituent containing at least one of an        aliphatic group, an aromatic group, hydroxy, alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro, nitroso, halogen        or hydrogen, provided that when X₁ to X₃ contain an aliphatic        group, the aliphatic group may be saturated or unsaturated,        substituted or unsubstituted, and straight, cyclic or branched,        and may contain at least one of oxygen, nitrogen, sulfur,        silicon, phosphorous, boron and halogen atoms; when X₁ to X₃        contain an aromatic group, the aromatic group may be substituted        or unsubstituted and may contain at least one of oxygen,        nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms;        when X₁ to X₃ contain hydroxy, the hydroxy may form a salt with        a metal atom; when X₁ to X₃ contain alkoxy, aldehyde, carboxyl,        alkoxycarbonyl, cyano, amino, nitro or nitroso, these        substituents may be substituted or unsubstituted and may contain        at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; X₁ to X₃ may be the same or different;        and X₁ to X₃ may form a ring.

In the above secondary battery, the radical compound may be a polymer.

The polymer may be, for example, a polymer having a polyacetylene orpolyphenylene-vinylene chain as a main chain.

In the above secondary battery, the radical compound may comprise an oxyradical compound.

The oxy radical compound may be, for example, an aryloxy radicalcompound.

Examples of the aryloxy radical compound may include those having anarylpolyoxy radical group, a tert-butyl group or a di-tert-butylphenoxyradical group.

In the above secondary battery, the oxy radical compound may be thatcontaining a semi-quinone.

In the above secondary battery, the oxy radical compound may be acompound which is poorly soluble in a basic solvent.

In the above secondary battery, the oxy radical compound may be apolymer radical compound.

Examples of the polymer radical compound may include compounds having apolyolefin, polyacetylene or polyphenylene structure. In particular,preferably used polymers may be those having a five-membered aromaticheterocyclic structure and polymer compounds having a three-dimensionalnetwork structure.

In the secondary battery, the radical compound may comprise a compoundhaving a radical on a nitrogen atom.

In the secondary battery, the radical compound may comprise a compoundhaving a radical on a nitrogen atom in an oxidized form.

In the secondary battery, the radical compound may comprise a compoundhaving a radical on a nitrogen atom in a reduced form.

Examples of the compound having a radical on a nitrogen atom mayinclude:

-   -   a compound having a radical on a trivalent pherdazyl group        represented by chemical formula (C1) or a tetravalent pherdazyl        group represented by chemical formula C (2);    -   a compound having a triphenylpherdazyl group represented by        chemical formula (C3) or (C4);    -   a compound having a radical on a trivalent hydrazyl group        represented by chemical formula (C5);    -   a compound having a radical on a trivalent hydrazyl group        represented by chemical formula (C6);    -   where R₁ to R₅ independently represent hydrogen, substituted or        unsubstituted aliphatic or aromatic hydrocarbon, halogen,        hydroxy, nitro, nitroso, cyano, alkoxy, aryloxy, alkoxycarbonyl,        aryloxycarbonyl, acyl or carboxy.

A compound having a radical on a nitrogen atom may bediphenylpicrylhydrazyl.

A compound having a radical on a nitrogen atom may be a compound havingan aminotriazine structure represented by general formula (C7):

-   -   where R₆ represents hydrogen, substituted or unsubstituted        aliphatic or aromatic hydrocarbon, halogen, hydroxy, nitro,        nitroso, cyano, alkoxy, aryloxy, alkoxycarbonyl,        aryloxycarbonyl, acyl, carboxy or oxo radical.

The compound having a radical on a nitrogen atom may be a polymer. Forexample, it may be a polymer having the aminotriazine structurerepresented by general formula (C7) as a repeating unit.

This invention also provides the following active materials for asecondary battery:

-   -   [1] an active material for a secondary battery comprising a        radical compound;    -   [2] an active material for a secondary battery involved in an        electrode reaction in the secondary battery, wherein a reactant        or product from the active material in the electrode reaction is        a radical compound.

In the above secondary battery, a spin concentration of the radicalcompound is 10²¹ spins/g or more.

The active material for a secondary battery may be used in a positiveelectrode in the secondary battery.

In the above active material for a secondary battery, the radicalcompound may contain a nitroxyl radical compound having the functionalgroup represented by chemical formula (A1).

In the above active material for a secondary battery, the radicalcompound may contain the nitroxyl radical compound represented bygeneral formula (A2):

-   -   wherein X₁ and X₂ are a substituent containing at least one of        an aliphatic group, an aromatic group, hydroxy, alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro,        nitroso, halogen or hydrogen, provided that when X₁ and X₂        contain an aliphatic group, the aliphatic group may be saturated        or unsaturated, substituted or unsubstituted, and straight,        cyclic or branched, and may contain at least one of oxygen,        nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms;        when X₁ and X₂ contain an aromatic group, the aromatic group may        be substituted or unsubstituted and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; when X₁ and X₂ contain hydroxy, the hydroxy may        form a salt with a metal atom; when X₁ and X₂ contain alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro or        nitroso, these substituents may be substituted or unsubstituted        and may contain at least one of oxygen, nitrogen, sulfur,        silicone, phosphorous, boron and halogen atoms; X₁ and X₂ may be        the same or different; and X₁ and X₂ taken together may form a        ring.

In the above active material for a secondary battery, the radicalcompound may be the nitroxyl radical compound in which a nitrogen atomin the nitroxyl radical is bound to at least one alkyl, represented bygeneral formula (A3):

-   -   wherein R is alkyl which may be substituted or unsubstituted,        straight, cyclic or branched, and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; X is a substituent containing at least one of an        aliphatic group, an aromatic group, hydroxy, alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro, nitroso, halogen        or hydrogen, provided that when X contains an aliphatic group,        the aliphatic group may be saturated or unsaturated, substituted        or unsubstituted, and straight, cyclic or branched, and may        contain at least one of oxygen, nitrogen, sulfur, silicon,        phosphorous, boron and halogen atoms; when X contains an        aromatic group, the aromatic group may be substituted or        unsubstituted and may contain at least one of oxygen, nitrogen,        sulfur, silicon, phosphorous, boron and halogen atoms; when X        contains hydroxy, the hydroxy may form a salt with a metal atom;        when X contains alkoxy, aldehyde, carboxyl, alkoxycarbonyl,        cyano, amino, nitro or nitroso, the substituent may be        substituted or unsubstituted and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; and X may form a ring.

In the above active material for a secondary battery, the alkyl groupmay be tert-butyl;

In the above active material for a secondary battery, the radicalcompound may be the nitroxyl radical compound in which a nitrogen atomin the nitroxyl radical is bound to at least two alkyls, represented bygeneral formula (A4):

-   -   wherein R_(1 and R) ₂ are alkyl which may be substituted or        unsubstituted, straight, cyclic or branched, and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; R_(1 and R) ₂ may be the same or        different; X₁ and X₂ are a substituent containing at least one        of an aliphatic group, an aromatic group, hydroxy, alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro,        nitroso, halogen or hydrogen, provided that when X₁ and X₂        contain an aliphatic group, the aliphatic group may be saturated        or unsaturated, substituted or unsubstituted, and straight,        cyclic or branched, and may contain at least one of oxygen,        nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms;        when X₁ and X₂ contain an aromatic group, the aromatic group may        be substituted or unsubstituted and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; when X₁ and X₂ contain hydroxy, the hydroxy may        form a salt with a metal atom; when X₁ and X₂ contain alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro or        nitroso, these substituents may be substituted or unsubstituted        and may contain at least one of oxygen, nitrogen, sulfur,        silicon, phosphorous, boron and halogen atoms; X₁ and X₂ may be        the same or different; and X₁ and X₂ may form a ring.

In the above active material for a secondary battery, both of the alkylsR₁ and R₂ may be methyl.

In the above active material for a secondary battery, the radicalcompound may be the nitroxyl radical compound in which a nitrogen atomin the nitroxyl radical is bound to two carbon atoms bound to at leasttwo alkyls, represented by general formula (A5):

-   -   wherein R₁ to R₄ are alkyl which may be substituted or        unsubstituted, straight, cyclic or branched, and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; R₁ to R₄ may be the same or different;        X₁ and X₂ are a substituent containing at least one of an        aliphatic group, an aromatic group, hydroxy, alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro, nitroso, halogen        or hydrogen, provided that when X₁ and X₂ contain an aliphatic        group, the aliphatic group may be saturated or unsaturated,        substituted or unsubstituted, and straight, cyclic or branched,        and may contain at least one of oxygen, nitrogen, sulfur,        silicon, phosphorous, boron and halogen atoms; when X₁ and X₂        contain an aromatic group, the aromatic group may be substituted        or unsubstituted and may contain at least one of oxygen,        nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms;        when X₁ and X₂ contain hydroxy, the hydroxy may form a salt with        a metal atom; when X₁ and X₂ contain alkoxy, aldehyde, carboxyl,        alkoxycarbonyl, cyano, amino, nitro or nitroso, these        substituents may be substituted or unsubstituted and may contain        at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; X₁ and X₂ may be the same or different;        and X₁ and X₂ may form a ring.

In the above active material for a secondary battery, all of the alkylsR₁ to R₄ may be methyl.

In the above active material for a secondary battery, the radicalcompound may be the nitroxyl radical compound in which a nitrogen atomin the nitroxyl radical is bound to at least one aryl, represented bygeneral formula (A6):

-   -   wherein Ar is aryl which may be substituted or unsubstituted and        may contain at least one of oxygen, nitrogen, sulfur, silicon,        phosphorous, boron and halogen atoms; X is a substituent        containing at least one of an aliphatic group, an aromatic        group, hydroxy, alkoxy, aldehyde, carboxyl, alkoxycarbonyl,        cyano, amino, nitro, nitroso, halogen or hydrogen, provided that        when X contains an aliphatic group, the aliphatic group may be        saturated or unsaturated, substituted or unsubstituted, and        straight, cyclic or branched, and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; when X contains an aromatic group, the aromatic        group may be substituted or unsubstituted and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; when X contains hydroxy, the hydroxy        may form a salt with a metal atom; when X contains alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro or        nitroso, the substituent may be substituted or unsubstituted and        may contain at least one of oxygen, nitrogen, sulfur, silicon,        phosphorous, boron and halogen atoms; and X may form a ring.

In the above active material for a secondary battery, the aryl may besubstituted or unsubstituted phenyl.

In the above active material for a secondary battery, the radicalcompound may form the substituted or unsubstituted heterocyclerepresented by general formula (A7):

-   -   wherein X is carbon, oxygen, nitrogen, sulfur, silicon,        phosphorous or boron atom, provided that X may be the same or        different; X may be bound via saturated or unsaturated bonds; X        may form a bond with any substituent; this compound may be a        polymer which may be straight, cyclic or branched; and n is an        integer of 2 to 10 both inclusive.

In the above active material for a secondary battery, the nitroxylradical compound may be that having a piperidinoxyl ring structurerepresented by general formula (A8):

-   -   where R₁ to R₄ are alkyl which may be substituted or        unsubstituted, straight, cyclic or branched, and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; X is a substituent containing at least        one of an aliphatic group, an aromatic group, hydroxy, alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro,        nitroso, halogen or hydrogen, provided that when X contains an        aliphatic group, the aliphatic group may be saturated or        unsaturated, substituted or unsubstituted, and straight, cyclic        or branched, and may contain at least one of oxygen, nitrogen,        sulfur, silicon, phosphorous, boron and halogen atoms; when X        contains an aromatic group, the aromatic group may be        substituted or unsubstituted and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; when X contains hydroxy, the hydroxy may form a        salt with a metal atom; when X contains alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro or nitroso, the        substituent may be substituted or unsubstituted and may contain        at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; and X may form a ring.

In the above active material for a secondary battery, the nitroxylradical compound may be that having a pyrrolidinoxyl ring structurerepresented by general formula (A9):

-   -   where R₁ to R₄ are alkyl which may be substituted or        unsubstituted, straight, cyclic or branched, and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; X is a substituent containing at least        one of an aliphatic group, an aromatic group, hydroxy, alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro,        nitroso, halogen or hydrogen, provided that when X contains an        aliphatic group, the aliphatic group may be saturated or        unsaturated, substituted or unsubstituted, and straight, cyclic        or branched, and may contain at least one of oxygen, nitrogen,        sulfur, silicon, phosphorous, boron and halogen atoms; when X        contains an aromatic group, the aromatic group may be        substituted or unsubstituted and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; when X contains hydroxy, the hydroxy may form a        salt with a metal atom; when X contains alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro or nitroso, the        substituent may be substituted or unsubstituted and may contain        at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; and X may form a ring.

In the above active material for a secondary battery, the nitroxylradical compound may be that having a pyrrolinoxyl ring structurerepresented by general formula (A10):

-   -   where R_(1 to R) ₄ are alkyl which may be substituted or        unsubstituted, straight, cyclic or branched, and may contain at        least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; X is a substituent containing at least        one of an aliphatic group, an aromatic group, hydroxy, alkoxy,        aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro,        nitroso, halogen or hydrogen, provided that when X contains an        aliphatic group, the aliphatic group may be saturated or        unsaturated, substituted or unsubstituted, and straight, cyclic        or branched, and may contain at least one of oxygen, nitrogen,        sulfur, silicon, phosphorous, boron and halogen atoms; when X        contains an aromatic group, the aromatic group may be        substituted or unsubstituted and may contain at least one of        oxygen, nitrogen, sulfur, silicon, phosphorous, boron and        halogen atoms; when X contains hydroxy, the hydroxy may form a        salt with a metal atom; when X contains alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro or nitroso, the        substituent may be substituted or unsubstituted and may contain        at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; and X may form a ring.

In the above active material for a secondary battery, the radicalcompound may be a compound forming a nitronylnitroxide structure,represented by general formula (A11):

-   -   where X₁ to X₃ are a substituent containing at least one of an        aliphatic group, an aromatic group, hydroxy, alkoxy, aldehyde,        carboxyl, alkoxycarbonyl, cyano, amino, nitro, nitroso, halogen        or hydrogen, provided that when X₁ to X₃ contain an aliphatic        group, the aliphatic group may be saturated or unsaturated,        substituted or unsubstituted, and straight, cyclic or branched,        and may contain at least one of oxygen, nitrogen, sulfur,        silicon, phosphorous, boron and halogen atoms; when X₁ to X₃        contain an aromatic group, the aromatic group may be substituted        or unsubstituted and may contain at least one of oxygen,        nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms;        when X₁ to X₃ contain hydroxy, the hydroxy may form a salt with        a metal atom; when X₁ to X₃ contain alkoxy, aldehyde, carboxyl,        alkoxycarbonyl, cyano, amino, nitro or nitroso, these        substituents may be substituted or unsubstituted and may contain        at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,        boron and halogen atoms; X₁ to X₃ may be the same or different;        and X₁ to X₃ may form a ring.

In the above active material for a secondary battery, the nitroxylradical compound may be a polymer compound.

In the above active material for a secondary battery, the polymercompound may be that having a polyacetylene chain as a main chain.

In the above active material for a secondary battery, the polymercompound may be that having a polyphenylene-vinylene chain as a mainchain.

In the above active material for a secondary battery, the radicalcompound may comprise an oxy radical compound.

In the above active material for a secondary battery, the oxy radicalcompound may be an aryloxy radical compound.

In the above active material for a secondary battery, the aryloxyradical compound may comprise arylpolyoxy radical group.

In the above active material for a secondary battery, the aryloxyradical compound may comprise a tert-butyl group.

In the above active material for a secondary battery, the aryloxyradical compound may comprise a di-tert-butylphenoxy radical group.

In the above active material for a secondary battery, the oxy radicalcompound may be that containing a semi-quinone.

In the above active material for a secondary battery, the oxy radicalcompound may be a compound which is poorly soluble in a basic solvent.

In the above active material for a secondary battery, the oxy radicalcompound may be a polymer radical compound.

In the above active material for a secondary battery, the polymerradical compound may be that having a polyolefin structure.

In the above active material for a secondary battery, the polymerradical compound may be that having a polyacetylene structure.

In the above active material for a secondary battery, the polymerradical compound may be that having a polyphenylene structure.

In the above active material for a secondary battery, the polymerradical compound may be that having a five-membered aromaticheterocyclic structure.

In the above active material for a secondary battery, the polymerradical compound may be that having a three-dimensional networkstructure.

In the above secondary battery, the radical compound may comprise acompound having a radical on a nitrogen atom.

In the above active material for a secondary battery, the radicalcompound may comprise a compound having a radical on a nitrogen atom inan oxidized form.

In the above active material for a secondary battery, the radicalcompound may comprise a compound having a radical on a nitrogen atom ina reduced form.

In the above active material for a secondary battery, the compoundhaving a radical on a nitrogen atom may be that having a radical on atrivalent pherdazyl group represented by chemical formula (C1) or atetravalent pherdazyl group represented by chemical formula C (2):

In the above active material for a secondary battery, the compoundhaving a radical on a nitrogen atom may be that having atriphenylpherdazyl group represented by chemical formula (C3) or (C4);

In the above active material for a secondary battery, the compoundhaving a radical on a nitrogen atom may be that having a radical on atrivalent hydrazyl group represented by chemical formula (C5):

In the above active material for a secondary battery, the compoundhaving a radical on a nitrogen atom may be that having a radical on atrivalent hydrazyl group represented by chemical formula (C6):

-   -   where R₁ to R₅ independently represent hydrogen, substituted or        unsubstituted aliphatic or aromatic hydrocarbon, halogen,        hydroxy, nitro, nitroso, cyano, alkoxy, aryloxy, alkoxycarbonyl,        aryloxycarbonyl, acyl or carboxy.

In the above active material for a secondary battery, the compoundhaving a radical on a nitrogen atom may be diphenylpicrylhydrazyl.

In the above active material for a secondary battery, the compoundhaving a radical on a nitrogen atom may be that having an aminotriazinestructure represented by general formula (C7):

-   -   where R₆ represents hydrogen, substituted or unsubstituted        aliphatic or aromatic hydrocarbon, halogen, hydroxy, nitro,        nitroso, cyano, alkoxy, aryloxy, alkoxycarbonyl,        aryloxycarbonyl, acyl, carboxy or oxo radical.

In the above active material for a secondary battery, the compoundhaving a radical on a nitrogen atom may be a polymer compound.

In the above active material for a secondary battery, the compoundhaving an aminotriazine structure may be a polymer compound having theaminotriazine structure represented by general formula (C7) as arepeating unit.

This invention provides a secondary battery on the basis of a novelmechanism that a radical compound is used as an electrode activematerial. When the radical compound consists of lighter materials suchas carbon, hydrogen and oxygen, it may be expected to provide asecondary battery with a high energy density per a weight. Furthermore,since only a radical site contributes a reaction in a secondary battery,this invention may provide a stable secondary battery whose cycleproperties are independent of diffusion of the active material. Inaddition, since a reactive unpaired electron is localized on a radicalatom in a radical compound, a concentration of the reactive site may beincreased to provide a large-capacity secondary battery. This inventionmay be suitably applied to a secondary battery or active material for asecondary battery which performs charge and discharge.

An electrode active material as used herein refers to a materialdirectly contributing to an electrode reaction such as charge anddischarge reactions, and plays a main role in a secondary batterysystem. An active material in this invention may be used as either apositive electrode or negative electrode active material, but it may bemore preferably used as a positive electrode active material because itis characterized by a light weight and has a good energy density incomparison with a metal oxide system.

In the light of stability, it is preferable that among electrodereactions in a positive electrode, an electrode reaction duringdischarge is that in which a radical compound is a reactant.Furthermore, when the reaction is that in which a reaction product mayform a bond with an electrolyte cation, much more improvement instability may be expected. Any type of electrolyte cations may be used,and in particular, a lithium ion is preferable in the light of acapacity.

As used herein, a reactant refers to a substance which is subject to achemical reaction and stably exists for a long time, while a productrefers to a substance formed as a result of a chemical reaction whichstable exists for a long time. In this invention, a reactant or productis a radical compound. This invention, therefore, does not encompass asystem in which a radical is formed for a quite short time as a reactionintermediate in the course of an electrode reaction.

According to a statistical mechanical theory, any chemical substancewould contain radical-form species at room temperature. In thisinvention, it is, however, important that radicals exist to an extentwhere they may function as an active material in a secondary battery.For example, U.S. Pat. No. 2,715,778 has indicated organic compoundssuch as polyaniline, polypyrrole, polythiophene and a disulfide as anelectrode active material, whose radical concentration is about 10¹⁸spin/g.

In contrast, a concentration of a radical compound in this invention ispreferably kept to 10¹⁹ spin/g or more, more preferably 10²¹ spin/g ormore, in the light of a capacity in a secondary battery.

In general, a radical concentration may be expressed as a spinconcentration That is, a spin concentration means the number of unpairedelectrons (radicals) per a unit weight, which is determined by, forexample, the following procedure from an absorption area intensity in anelectron spin resonance spectrum (hereinafter, referred to as an “ESR”spectrum). First, a sample to be measured by ESR spectroscopy ispulverized by grinding it in, for example, a mortar, whereby the samplemay be ground to a particle size in which skin effect, i.e., aphenomenon that microwave does not penetrate a sample, can be ignored. Agiven amount of the pulverized sample is filled in a quartz glasscapillary with an inner diameter of 2 mm or less, preferably 1 to −0.5mm, vacuumed to 10-5 mmHg or less, sealed and subject to ESRspectroscopy. ESR spectroscopy may be conducted using an apparatus suchas Model JEOL-JES-FR30 ESR spectrometer. A spin concentration may bedetermined by integrating twice an ESR signal obtained and comparing itto a calibration curve. There are no restrictions to a spectrometer ormeasuring conditions as long as a spin concentration can be accuratelydetermined. As described above, a spin concentration for a radicalcompound may be evaluated by, for example, electron spin resonancespectroscopy. A charge state in a radical compound is preferably neutralin the light of easy charge/discharge reactions. For stability of asecondary battery, a radical compound is desirably stable. A stableradical as used herein refers to a compound whose radical form has along life. A longer radical life is better, but it depends on variousfactors such as reactivity of the radical itself and ambient conditionssuch as a solvent.

A radical is a chemical species with an unpaired electron and a compoundhaving the chemical species is a radical compound. A radical isgenerally highly reactive and is frequently an unstable speciesgenerated as an intermediate in a variety of reactions. Such an unstableradical forms a bond with a surrounding substance present in a reactionsystem and disappears in a certain life.

Some of stable radicals, however, do not form a bond with a surroundingsubstance and stably exist for a relatively longer period. Thesecompounds stabilize a radical by steric hindrance with an organicprotective group or delocalization of a

-electron. An electrode active material of this invention utilizes sucha compound generally exhibiting a spin concentration of 10¹⁹ to 10²³spins/g determined by electron spin resonance spectroscopy for a longperiod, e.g., 1 sec or longer.

In particular, a stable radical compound herein is a compound in which aspin concentration of 10²¹ spins/g or more in an equilibrium state iskept for 1 sec or longer.

A radical compound herein is a compound having an unpaired electron as auncombined hand and thus does not encompass a transition metal compoundhaving a stable unpaired electron in its inner shell.

Generally, an electrode active material in a secondary battery may takeeither an oxidized or reduced form depending on its starting state andan electrode reaction, and this invention is wherein the active materialcomprises a radical compound either in a starting state or in anoxidized or reduced state. A charge/discharge mechanism is not clearlyunderstood, but may be assumed that a radical group in an activematerial would be reversibly changed into a radical or ion state by anelectrode reaction for accumulating charge. Furthermore, this inventionis wherein an oxy radical compound directly contributes to an electrodereaction in a positive electrode or negative electrode, and therefore,an electrode used as an active material is not limited to one of thepositive electrode and the negative electrode. A radical compound is,however, preferably used as an electrode active material in a positiveelectrode in the light of an energy density. For stability, an electrodereaction during discharge among electrode reactions in a positiveelectrode is that in which a radical compound is a reactant.Furthermore, when a product in this reaction forms a bond with a cationof an electrolyte salt, further improvement in stability may beexpected. There are herein no restrictions to the electrolyte cation,but a lithium ion is preferable in the light of a capacity.

Examples of a radical compound in this invention include a compoundhaving a nitroxyl radical group, an oxy radical compound, a compoundhaving a sulfur radical, a compound having a radical on its nitrogenatom and a compound having a carbon radical.

Nitroxyl Radical Compound

A nitroxyl radical compound particularly exhibits good radicalstability. A nitroxyl radical compound refers to a compound having anitroxyl radical group represented by formula (A1).

A nitroxyl radical group is a substituent in which an oxygen atomforming a nitroxide group having a bond between the oxygen and nitrogenhas an unpaired electron. Generally, a radical compound is a highlyreactive chemical species. It is, therefore, frequently unstable andinteracts with a surrounding material to disappear within a certainlife. A nitroxyl radical compound is, however, wherein the unpairedelectron on the oxygen atom is stabilized by an electroattracting groupon the nitrogen atom.

Oxy Radical Compound

An oxy radical compound is a compound having a substituent comprising anoxygen atom having an unpaired electron. Generally, a oxy radical is ahighly reactive chemical species. It is, therefore, frequently unstableand interacts with a surrounding material to disappear within a certainlife, but may be stable depending on resonance effect, steric hindranceand solvation conditions. Some of these stable oxy radical compounds mayexhibit a spin concentration of 10¹⁹ to 10²³ spins/g determined byelectron spin resonance spectroscopy for a long time.

When an oxy radical compound consists of lighter materials such ascarbon, hydrogen and oxygen, a secondary battery with an energy densityper a unit weight may be provided. Furthermore, since only an oxyradical site contributes to a reaction in a secondary battery accordingto this invention, the battery may be stable without dependency of cycleproperties on diffusion of an active material. In addition, an unpairedelectron which reacting as an electrode active material is localized ona radical atom in an oxy radical compound, so that a concentration ofthe oxy radical as a reaction site can be increased to provide alarge-capacity secondary battery with a higher energy density.

Compound Having a Radical on a Nitrogen Atom

A compound having a radical on a nitrogen atom is a compound having asubstituent comprising a nitrogen atom having an unpaired electron.Generally, a radical is a highly reactive chemical species. It is,therefore, frequently unstable and interacts with a surrounding materialto disappear within a certain life, but may be stable depending onresonance effect, steric hindrance and solvation conditions. Some ofthese stable compounds having a radical on a nitrogen atom may exhibit aspin concentration of 10¹⁹ to 10²³ spins/g determined by electron spinresonance spectroscopy for a long time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating an embodiment of a secondary batteryconfiguration according to this invention.

FIG. 2 is a cross section illustrating an embodiment of a secondarybattery configuration according to this invention.

FIG. 3 shows discharge curves for a secondary battery determined inExamples 1 to 3 according to this invention and Comparative Example 1.

FIG. 4 shows a charge/discharge curve determined in Example 1 accordingto this invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Materials Constituting an Electrode

A secondary battery according to this invention may

-   -   (i) use a material comprising a radical compound as an active        material, or    -   (ii) utilize an electrode reaction in which a radical compound        is a reactant or product.

The electrode reaction in the above (ii) may be a discharge reaction inwhich a radical compound is a reactant or product. A discharge reactionin which a radical compound is a reactant may be, for example, thatforming a bond between a radical compound and an electrolyte cation. Adischarge reaction in which a radical compound is a product may be, forexample, that cleaving a bond between a radical compound and anelectrolyte cation.

Examples of a radical compound used in this invention include thenitroxyl radical compounds represented by chemical formulas 1 to 3; thepolymer nitroxyl radical compounds represented by chemical formulas 4 to6; the phenoxyl radical compounds represented by chemical formulas 7 and8; the polymer phenoxyl radical compounds represented by chemicalformulas 9 and 10; the hydrazyl radical compounds represented bychemical formulas 11 to 13; the hydrazyl radical compounds representedby chemical formulas 14 and 15; carbon radical compounds; sulfur radicalcompounds; and boron radical compounds. It may be a low-molecular weightor polymer compound. It may be a polymer compound in which one of theabove compound is present. Furthermore, two or more radical compoundsmay be mixed. As shown in chemical formula 16, a substance forming aradical compound by releasing lithium by charging may be used.

A polymer compound as used herein is an aggregate of polymers having alarge molecular weight, exhibiting insolubility in a variety of solventsdue to its intermolecular interaction compared to a low molecular weightcompound. Therefore, when a secondary battery is formed using a polymerradical compound, elution from an electrode may be minimized to providegood stability. It is necessary in this invention that a radicalcompound as an active material is retained on the electrode duringcharging/discharging. The radical compound is, therefore, preferablyinsoluble in a basic solvent constituting an electrolyte solution.However, when forming a large-capacity secondary battery, the amount ofan electrolyte or electrolyte solution to an active material is so smallthat an insoluble radical compound with a solubility of about 1 g orless (the amount (grams) of a solute to 100 g of a solvent) may bestably retained on the electrode.

In this invention, a radical compound as an active material is used inboth or one of a positive electrode and a negative electrode layers.When using it in one of the layers, a well known material as an activematerial in a secondary battery may be used in the other electrodelayer. Examples of such a conventional material include, metal oxideparticles, disulfide compounds and conductive polymers as a positiveelectrode layer when using a radical compound in a negative electrodelayer. Herein, examples of a metal oxide include lithium manganate orlithium manganate with a spinel structure such as LiMnO₂ and Li_(x)Mn₂O₄(0<x<2), MnO₂, LiCoO₂, LiNiO₂ and Li_(x)V₂O₅ (0<x<2). Examples of aconductive polymer include polyacetylene, polyphenylene, polyaniline andpolypyrrole.

In this invention, these materials for a positive electrode layer may beused alone or in combination of two or more. A radical compound may bemixed with a known active material to be used as a complex activematerial.

On the other hand, when using a radical compound in a positiveelectrode, examples of a material for a negative electrode layer includecarbon materials such as graphite and amorphous carbon, lithium metal ora lithium alloy, lithium-ion occluding carbon and conductive polymers.These materials may take an appropriate form such as film, bulk,granulated powder, fiber and flake.

In this invention, a conductive auxiliary material or ion-conductiveauxiliary material may be added for reducing an impedance during formingan electrode layer comprising a radical compound. Examples of such amaterial include carbonaceous particles such as graphite, carbon blackand acetylene black and conductive polymers such as polyaniline,polypyrrole, polythiophene, polyacetylene and polyacene as a conductiveauxiliary material as well as a gel electrolyte and a solid electrolyteas an ion-conductive auxiliary material.

In this invention, a binder may be used for reinforcing binding betweencomponents. Examples of a binder include polyvinylidene fluoride, acopolymer of vinylidene fluoride and hexafluoropropylene, a copolymer ofvinylidene fluoride and tetrafluoroethylene, polytetrafluoroethylene, acopolymer rubber of styrene and butadiene, and resin binders such aspolypropylene, polyethylene and polyimide.

In this invention, a catalyst may be used for accelerating an electrodereaction. Examples of a catalyst include conductive polymers such aspolyaniline, polypyrrole, polythiophene, polyacetylene and polyacene;basic compounds such as pyridine derivatives, pyrrolidone derivatives,benzimidazole derivatives, benzothiazole derivatives and acridinederivatives; and metal-ion complexes.

This invention is characterized in that an active material in at leastone of a positive electrode and a negative electrode comprises a radicalcompound, but there are no restrictions to its amount. However, since acapacity as a secondary battery depends on the amount of the radicalcompound contained, the content is desirably 1 wt % or more forachieving adequate effects of this invention. The content lower than thelimit may lead to inadequate effects of this invention of a higherenergy density and a larger capacity.

Structure of a Second Battery

A secondary battery according to this invention has a configuration, forexample, as shown in FIG. 1, where a negative electrode layer 1 and apositive electrode layer 2 are piled via a separator 5 containing anelectrolyte. In this invention, an active material used in the negativeelectrode layer 1 or the positive electrode layer 2 is a radicalcompound.

FIG. 2 is a cross section of a laminated secondary battery, where apositive electrode collector 4, a positive electrode layer 2, aseparator 5 containing an electrolyte, a negative electrode layer 1 anda negative electrode collector 3 are piled in sequence. In thisinvention, a positive electrode and a negative electrode layers may bepiled as appropriate; for example, the secondary battery may be amulti-layer laminate, a combination of collectors with layers on bothsides and a rolled laminate.

The negative electrode collector 3 and the positive electrode collector4 may be a metal foil or metal plate made of, for example, nickel,aluminum, copper, gold, silver, an aluminum alloy and stainless steel; amesh electrode; and a carbon electrode. The collector may be active as acatalyst or an active material may be chemical bound to a collector. Aseparator made of a porous film or a nonwoven fabric may be used forpreventing the above positive electrode from being in contact with thenegative electrode.

An electrolyte contained in the separator 5 transfers charged carriersbetween the electrodes, i.e., the negative electrode 1 and the positiveelectrode 2, and generally exhibits an electrolyte-ion conductivity of10⁻⁵ to 10⁻¹ S/cm at room temperature. An electrolyte used in thisinvention may be an electrolyte solution prepared by, for example,dissolving an electrolyte salt in a solvent. Examples of such a solventinclude organic solvents such as ethylene carbonate, propylenecarbonate, dimethyl carbonate, diethyl carbonate, methyl ethylcarbonate, γ-butyrolactone, tetrahydrofurane, dioxolane, sulforane,dimethylformamide, dimethylacetamide and N-methyl-2-pyrrolidone. In thisinvention, these solvents may be used alone or in combination of two ormore. Examples of an electrolyte salt include LiPF₆, LiClO₄, LiBF₄,LiCF₃SO₃, LiN(CF₃SO₂)₂, LiN(C₂F₅SO₂)₂, LiC(CF₃SO₂)₃ and LiC(C₂F₅SO₂)₃.

An electrolyte may be solid. Examples of a polymer used in the solidelectrolyte include vinylidene fluoride polymers such as polyvinylidenefluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, acopolymer of vinylidene fluoride and ethylene, a copolymer of vinylidenefluoride and monofluoroethylene, a copolymer of vinylidene fluoride andtrifluoroethylene, a copolymer of vinylidene fluoride andtetrafluoroethylene and a terpolymer of vinylidene fluoride,hexafluoropropylene and tetrafluoroethylene; acrylonitrile polymers sucha copolymer of acrylonitrile and methyl methacrylate, a copolymer ofacrylonitrile and methyl acrylate, a copolymer of acrylonitrile andethyl methacrylate, a copolymer of acrylonitrile and ethyl acrylate, acopolymer of acrylonitrile and methacrylic acid, a copolymer ofacrylonitrile and acrylic acid and a copolymer of acrylonitrile andvinyl acetate; polyethylene oxide; a copolymer of ethylene oxide andpropylene oxide; and polymers of these acrylates or methacrylates. Thepolymer may contain an electrolyte solution to form a gel or the polymermay be used alone.

A secondary battery in this invention may have a conventionalconfiguration, where, for example, an electrode laminate or rolledlaminate is sealed in, for example, a metal case, a resin case or alaminate film made of a metal foil such as aluminum foil and a syntheticresin film. It may take a shape of, but not limited to, cylindrical,prismatic, coin or sheet.

A secondary battery according to this invention may be prepared by aconventional process. For example, a slurry of an active material in asolvent is applied on an electrode laminate and the product is piledwith a counter electrode via a separator. Alternatively, the laminate isrolled and placed in a case, which is then filled with an electrolytesolution. A secondary battery may be prepared using a radical compounditself or using a compound which can be converted into a radicalcompound by a redox reaction. Examples of a compound which can beconverted into a radical compound by a redox reaction include a lithiumor sodium salt of an anion generated by reduction of a radical compound.In this invention, a secondary battery may be prepared using a compoundwhich can be converted into a radical compound as a result of a redoxreaction.

Nitroxyl Radical Compound

A nitroxyl radical compound in this invention has a nitroxyl radicalgroup in a molecular structure. Chemical formulas A12 to A49 showsspecific examples of a nitroxyl radical compound.

A compound in which a bulky alkyl group is attached to a nitrogen atomforming a nitroxyl radical group is expected to be highly stable becauseof its steric hindrance. Such an alkyl is preferably tert-butyl.Chemical formulas (A12) to (A19) are examples of a compound in which atert-butyl group is attached to a nitrogen atom forming a nitroxylradical group.

In the light of stability in a radical, it is preferable that a carbonatom to which at least two alkyl groups are attached is bound to anitrogen atom forming a nitroxyl radical group. In particular, when thenitrogen atom is bound to two carbon atoms to each of which at least twoalkyl groups are attached, it may be expected that a more stable radicalcompound is provided. The alkyl group herein is preferably methyl.Chemical formulas (A12) to (A20) and (A24) to (A48) show examples of acompound in which a carbon atom to which two methyl groups are attachedis bound to a nitrogen atom forming a nitroxyl radical group.

A compound in which an aryl group is attached to a nitrogen atom forminga nitroxyl radical group is expected to be more stable because ofelectron delocalization. The aromatic group herein is preferably asubstituted or unsubstituted phenyl group in the light of stability.Chemical formulas (A13) to (A19) and (A21) and (A22) show examples of acompound in which an aryl group is attached to a nitrogen atom forming anitroxyl radical group.

When a nitrogen atom forming a nitroxyl radical group is one member of aheterocycle, it may be expected that stability of a radical is improvedbecause it may inhibit an intramolecular reaction of the nitroxylradical group. The heterocycle herein is preferably a piperidinoxy,pyrrolidinoxy or pyrrolinoxy ring in the light of stability. Chemicalformulas (A23) to (A48) show examples of a compound in which a nitrogenatom forming a nitroxyl radical group is one member of a heterocycle;specifically, chemical formulas (A26) to (A30) for a piperidinoxy ring,chemical formulas (A31) to (A36) for a piperidinoxy ring and chemicalformulas (A37) to (A41) for a piperidinoxy ring.

When a nitroxyl radical group forms a nitroxylnitroxide structure, itmay be expected that a radical is more stable because of electrondelocalization. Chemical formulas (A43) to (A48) show examples of acompound having a nitroxylnitroxide structure.

A compound in which a nitroxy radical compound is a polymer compound ispreferable because it is resistant to dissolving by an electrolytesolution to give good stability without deterioration for a long time.Such a polymer compound may be straight, cyclic or branched.Furthermore, a compound having a polyacetylene or polyphenylene vinylenechain as a main chain may be highly stable because of electronicdelocalization.

A nitroxyl radical compound as an active material in a secondary batteryaccording to this invention may be a solid or a solution, without anyrestriction in terms of operation. It is, however, preferably insolublein a basic solvent in the light of a rate and an efficiency incharge/discharge. There are no restrictions to a molecular weight of anitroxyl radical compound in this invention, and a variety of molecularweight may be thus acceptable from a compound with a low molecularweight to a polymer compound. However, a polymer is preferable in thelight of stability of its charged or discharged state, particularly apolymer radical having a polyacetylene or polyphenylene structure.Examples of a compound in which a nitroxyl radical compound forms apolymer compound are shown in chemical formulas (A16) to (A20), (A22),(A25), (A29), (A30), (A42) and (A46) to (A48). Specifically, chemicalformulas (A16), (A17), (A22), (A29), (A30) and (A46) show examples of acompound having a polyacetylene chain as a main chain while chemicalformulas (A18), (A19) and (A47) show examples of a compound having apolyphenylene vinylene chain as a main chain.

Oxy Radical Compound

An oxy radical compound used in this invention has an oxy radical groupin its molecular structure. It preferably has an aryloxy radical groupor semiquinone in the light of stability of a radical state.

Examples of an oxy radical compound are shown below.

A compound having an aryloxy radical indicates an aromatic compound suchas benzene, naphthalene and thiophene having an oxy radical group, whilea compound having semiquinone indicates a structure formed by incompletecombustion of a benzenoid and a quinoid compounds. A compound having anaryloxy radical compound is preferably that having an arylpolyoxyradical group or a tertiary butyl group. A compound having a tertiarybutyl group is that having a di-tert-butylphenoxy radical group.Examples of a compound having an aryloxy radical group are those shownin chemical formula B1 to 3 and their derivatives. Examples of acompound having an arylpolyoxy radical group are that shown in chemicalformula B4 and its derivatives. Examples of an aryloxy radical compoundhaving a di-tert-butyl group are those shown in chemical formulas B5 to8 and their derivatives. Examples of a semiquinone are that shown inchemical formula B9 and its derivatives.

An oxy radical compound as an active material in a secondary batteryaccording to this invention may be a solid or a solution, without anyrestriction in terms of operation. It is, however, preferably insolublein a basic solvent in the light of a rate and an efficiency incharge/discharge. There are no restrictions to a molecular weight of anoxy radical compound in this invention, and a variety of molecularweight may be thus acceptable from a compound with a low molecularweight to a polymer compound. However, a polymer is preferable in thelight of stability of its charged or discharged state, particularly apolymer radical compound having a polyolefin, polyacetylene,polyphenylene or five-membered aromatic heterocycle structure, mostpreferably a polymer radical compound having a three-dimensional networkstructure. Examples of a compound having a polyolefin structure are thepolymer compounds shown in chemical formulas B10 to 11 and theirderivatives. Examples of a compound having a polyacetylene structure arethe polymer compounds shown in chemical formulas B12 to 15 and theirderivatives. Examples of a compound having a polyphenylene structure arethe polymer compounds shown in chemical formulas B16 to 20 and theirderivatives. Examples of a compound having a five-membered aromaticheterocycle structure are the polymer compounds shown in chemicalformulas B21 to 23 and their derivatives. Examples of a compound havinga three-dimensional network structure are the compound shown in chemicalformula B24 and its derivatives. Compound having a radical on a nitrogenatom A compound having a radical on a nitrogen atom used as an activematerial in this invention has a radical on a nitrogen atom in itsmolecular structure. Examples of the compound include those having aradical on an amino group as described in O. Shimamura et al., “YurikiHannou”, Tokyo Kagaku Dojin, pp. 24-34 (1964); the compound having aradical on a pherdazyl group represented by chemical formula (C8):

-   -   the compound having a radical on a hydrazyl group represented by        chemical formula (C9):    -   polymer compounds as described in S. Okawara, “Kobunshi no        Kagaku Hannou”, Kagaku Dojin, pp. 340-346 (1972).

More specific examples include the lophine derivative represented bychemical formula (C10); the tetraphenylpyrrole derivative represented bychemical formula (C11); the phenothiazine derivative represented bychemical formula (C12); 2,2-diphenyl-1-picrylhydrazyl represented bychemical formula (C13); the1,1,5,5-tetraphenyl-1,2,4,5-tetraaza-2-pentene derivative represented bychemical formula (C14); 1,3,5-triphenylpheldazyl represented by chemicalformula (C15); the compounds having a triphenylpheldazyl grouprepresented by chemical formulas (C16) and (C17); the polymer compoundshaving a triphenylpheldazyl group represented by chemical formulas (C18)to (C25); and the polymer compounds having an aminotriazine structurerepresented by chemical formulas (C26) to (C28).

In the above foumulae, n represents an integer of 1 to 8;

In the above foumula C25, R represents, e.g., an alkylene or aromaticgroup;

In this invention, there are no restrictions to a molecular weight of acompound having a radical on a nitrogen atom and thus a compound with alow molecular weight from a polymer compound may be used as necessary. Apolymer compound generally has a lower solubility in an electrolytesolution compared with a compound with a low molecular weight, so that acapacity reduction due to dissolution in the electrolyte solution issmaller. Examples of a polymer compound include those having any of thestructures represented by chemical formulas C18 to C28, C31 and C32, aswell as polymer compounds having a polyolefin, polyacetylene,polyphenylene or five-membered aromatic heterocycle structure. Thepolymer compound may have a three-dimensional network structure. Acompound having a radical on a nitrogen atom as an active material in asecondary battery in this invention may be solid or may be dissolved ordispersed in an electrolyte. When using as a solid, it may be preferablyinsoluble or poorly soluble in an electrolyte solution because capacityreduction due to dissolution in an electrolyte solution may beminimized. A compound having a radical on a nitrogen atom as an activematerial in a secondary battery in this invention is generally usedalone, or in combination of two or more or another type of activematerial.

EXAMPLES

This invention will be more specifically described with reference toExamples.

The compounds used in Examples 1 to 5 are as follows.

Example 1

In a dry box equipped with a gas purifier were mixed 60 mg of acopolymer of vinylidene fluoride and hexafluoropropylene and 140 mg ofan electrolyte solution which was a 1:1 mixture of ethylenecarbonate/propylene carbonate containing 1 mol/L of LiPF₆ electrolytesalt under an atmosphere of argon gas. To the mixture was added 1130 mgof tetrahydrofuran, and the mixture was dissolved to prepare a solutionof a gel electrolyte in tetrahydrofuran.

In a separate glass vessel was placed 30 mg of2,2,6,6-tetramethylpiperidoxyl radical (TEMPO radical) having themolecular structure represented by chemical formula 1, which is anitroxyl radical compound, as a radical compound, then 60 mg of graphitepowder as a conductive adjuvant and then 200 mg of the above solution ofa gel electrolyte in tetrahydrofuran as an ion-conductive adjuvant, andthe mixture was blended. To the mixture was added 1000 mg oftetrahydrofuran and the mixture was further blended until it becamehomogeneous to provide a black slurry. Then, 200 mg of the slurry wasadded dropwise on the surface of an aluminum foil (area: 1.5 cm×1.5 cm,thickness: 100 μm) with a lead, and the slurry was spread using a wirebar such that the overall surface became even. It was left for 60 min atroom temperature to evaporate the solvent, tetrahydrofuran, and to forman organic compound layer containing TEMPO radical on the aluminum foil.

An aliquot of the applied film was taken, ground and subject to electronspin resonance spectroscopy. A spin concentration was determined withModel JEOL-JES-FR30 ESR spectrometer under the conditions of a microwavepower of 4 mW, a modulation frequency of 100 kHz and a modulation widthof 79 μT in a range of 335.9 mT±5 mT. An absorption area intensity wasdetermined by integrating twice a first derivation type of ESR spectrumobtained as described above and compared with an absorption areaintensity for a known sample measured under the same conditions todetermine a spin concentration. As a result, a spin concentration was10²¹ spin/g or higher, indicating formation of a radical in an initialstate.

To 600 mg of a copolymer of vinylidene fluoride and hexafluoropropylenewere added 1400 mg of the 1:1 mixture of ethylene carbonate/propylenecarbonate containing 1 mol/L of LiPF₆ electrolyte salt and then 11.3 gof tetrahydrofuran, and the mixture was stirred at room temperature.After dissolving the copolymer of vinylidene fluoride andhexafluoropropylene, the mixture was applied on a stepped glass plate toa thickness of 1 mm. It was left for 1 hour for spontaneous evaporationof tetrahydrofuran to provide a gel electrolyte film with a thickness of150 μm on the glass plate.

The gel electrolyte film cut by 2.0 cm×2.0 cm was laminated on thealuminum foil on which an organic compound layer containing TEMPOradical had been formed. On the foil was then laminated a copper foilhaving a lithium film with a lead (thickness: 30 μm for the lithium filmand 20 μm for the copper foil). The whole product was sandwiched withpolytetrafluoroethylene sheets with a thickness of 5 mm and was pressedto provide a secondary battery.

For the secondary battery thus prepared, discharge with a constantcurrent of 0.1 mA was conducted using the aluminum foil with an organiccompound layer containing TEMPO radical as a positive electrode and thecopper foil with a lithium film as a negative electrode. The results areillustrated in FIG. 3, in which a voltage plateau can be found at about2.3 V, indicating that the battery acted as a secondary battery. A partof the compound layer containing TEMPO radical was removed from thesample after discharge and it was subject to electron spin resonancespectroscopy as described above to give a spin concentration of 10¹⁹spin/g or less. It indicates that after discharge, TEMPO radical formeda bond with lithium ion, leading to absence of effective radicals for aredox reaction.

Another secondary battery prepared as described above was evaluated forvoltage variation in association with charge/discharge. The resultsobtained after 10 cycles of charge/discharge are illustrated in FIG. 4,in which a plateau is seen in a discharge curve after repeatedcharge/discharge, indicating that the battery also acted as a secondarybattery.

Secondary batteries were prepared using the polymer compoundsrepresented by chemical formulas 2, 3 and 4 to 6 in place of TEMPOradical in Example 1 as a nitroxyl radical compound. They also acted asa secondary battery as described in Example 1.

Comparative Example 1

In a glass vessel in Example 1 were mixed a conductive adjuvant, anion-conductive adjuvant, a mixed solution of ethylene carbonate andpropylene carbonate and tetrahydrofuran to prepare a black slurry asdescribed in Example 1 except that TEMPO radical was absent. Then, on analuminum foil was formed a compound layer without TEMPO radical asdescribed in Example 1. A part of the layer was removed and subject toelectron spin resonance spectroscopy as described in Example 1 to give aspin concentration of 10¹⁹ spin/g or less, indicating a smaller radicalconcentration.

The gel electrolyte film in Example 1 was laminated on the aluminum foilon which a compound layer without TEMPO radical had been formed andfurther a copper foil having a lithium film in Example 1 was laminated.The whole product was sandwiched with polytetrafluoroethylene sheets andwas pressed as described in Example 1 to provide a secondary battery.

For the secondary battery thus prepared, discharge with a constantcurrent of 0.1 mA was conducted using the aluminum foil without acompound layer without TEMPO radical as a positive electrode and thecopper foil with a lithium film as a negative electrode. The results areillustrated in FIG. 3. The battery did not exhibited behavior as asecondary battery. When attempting charge by applying a constant currentof 0.1 mA, a voltage momentarily exceeded 3.0 V and after discharge aplateau was not observed in a voltage curve. It indicated that thebattery with this configuration did not act as a secondary battery.

Example 2

In a glass vessel in Example 1 were mixed a conductive adjuvant, anion-conductive adjuvant, a mixed solution of ethylene carbonate andpropylene carbonate and tetrahydrofuran to prepare a black slurry asdescribed in Example 1 except that TEMPO radical was substituted withgalvinoxyl radical having the molecular structure represented bychemical formula 7, a phenoxyl radical compound. Then, on an aluminumfoil was formed a compound layer containing galvinoxyl radical asdescribed in Example 1. A part of the layer was removed and subject toelectron spin resonance spectroscopy as described in Example 1 to give aspin concentration of 10²¹ spin/g or more, indicating that a radical wasformed in an initial state.

On the aluminum foil having the compound layer containing galvinoxylradical were sequentially laminated the gel electrolyte film in Example1 and the copper foil with a lithium film. Then, the whole product wassandwiched with polytetrafluoroethylene sheets and pressed to prepare asecondary battery as described in Example 1.

For the secondary battery thus prepared, discharge with a constantcurrent of 0.1 mA was conducted using the aluminum foil with a compoundlayer containing galvinoxyl radical as a positive electrode and thecopper foil with a lithium film as a negative electrode. The results areillustrated in FIG. 3, in which voltage plateaus can be found at about2.3 V, 2.0 V and 1.5 V, indicating that the battery acted as a secondarybattery. A part of the compound layer containing galvinoxyl radical wasremoved from the sample after discharge and it was subject to electronspin resonance spectroscopy as described in Example 1 to give a spinconcentration of 10¹⁹ spin/g or less. It indicates that after discharge,galvinoxyl radical formed a bond with lithium ion, leading to absence ofeffective radicals for a redox reaction.

Voltage variation in association with charge/discharge was evaluated asdescribed in Example 1. The results obtained indicated that the batterycould be repeatedly charged/discharged and also acted as a secondarybattery.

Secondary batteries were prepared using the polymer compoundsrepresented by chemical formulas 8, 9 and 10 in place of galvinoxylradical used in Example 2 as a phenoxyl radical compound. They alsoacted as a secondary battery as described in Example 2.

Example 3

In a glass vessel in Example 1 were mixed a conductive adjuvant, anion-conductive adjuvant, a mixed solution of ethylene carbonate andpropylene carbonate and tetrahydrofuran to prepare a black slurry asdescribed in Example 1 except that TEMPO radical was substituted with2,2-diphenyl-1-picrylhydrazyl radical (DPPH radical) having themolecular structure represented by chemical formula 11, a hydrazylradical compound.

Then, on an aluminum foil was formed a compound layer containing DPPHradical as described in Example 1. A part of the layer was removed andsubject to electron spin resonance spectroscopy as described in Example1 to give a spin concentration of 10²¹ spin/g or more, indicating that aradical was formed in an initial state.

On the aluminum foil having the compound layer containing DPPH radicalwere sequentially laminated the gel electrolyte film in Example 1 andthe copper foil with a lithium film. Then, the whole product wassandwiched with polytetrafluoroethylene sheets and pressed to prepare asecondary battery as described in Example 1.

For the secondary battery thus prepared, discharge with a constantcurrent of 0.1 mA was conducted using the copper foil with a compoundlayer containing DPPH radical as a positive electrode and the copperfoil with a lithium film as a negative electrode. The results areillustrated in FIG. 3, in which voltage plateaus can be found at about3.1 V and 2.5 V, indicating that the battery acted as a secondarybattery. A part of the compound layer containing DPPH radical wasremoved from the sample after discharge and it was subject to electronspin resonance spectroscopy as described in Example 1 to give a spinconcentration of 10¹⁹ spin/g or less. It indicates that after discharge,DPPH radical formed a bond with lithium ion, leading to absence ofeffective radicals for a redox reaction.

Voltage variation in association with charge/discharge was evaluated asdescribed in Example 1. The results obtained indicated that the batterycould be repeatedly charged/discharged and also acted as a secondarybattery.

Secondary batteries were prepared using the polymer compoundsrepresented by chemical formulas 12, 13, 14 and 15 in place of DPPHradical used in Example 3 as a hydrazyl radical compound. They alsoacted as a secondary battery as described in Example 3.

Example 4

In a glass vessel in Example 1 were mixed a conductive adjuvant, anion-conductive adjuvant, a mixed solution of ethylene carbonate andpropylene carbonate and tetrahydrofuran to prepare a black slurry asdescribed in Example 1 except that TEMPO radical was substituted withlithium 2,4,6-tri-tert-butylphenoxide having the molecular structurerepresented by chemical formula 16. Then, on an aluminum foil was formeda compound layer containing lithium 2,4,6-tri-tert-butylphenoxide asdescribed in Example 1. A part of the layer was removed and subject toelectron spin resonance spectroscopy as described in Example 1 to give aspin concentration of 10¹⁹ spin/g or less, indicating that there were noradicals in an initial state.

On the aluminum foil having the compound layer containing lithium2,4,6-tri-tert-butylphenoxide were sequentially laminated the gelelectrolyte film in Example 1 and the copper foil with a lithium film.Then, the whole product was sandwiched with polytetrafluoroethylenesheets and pressed to prepare a secondary battery as described inExample 1.

For the secondary battery thus prepared, discharge with a constantcurrent of 0.1 mA was conducted using the copper foil with a compoundlayer containing lithium 2,4,6-tri-tert-butylphenoxide as a positiveelectrode and the copper foil with a lithium film as a negativeelectrode. When the battery voltage became 3.0 V, the voltage was keptconstant. Then charge was terminated when a current value became 0.01mA. After a 5 min interval, discharge was restarted to obtain adischarge curve. In the curve, a plateau can be found at about 2.3 V,indicating that the battery acted as a secondary battery. A part of thecompound layer containing lithium 2,4,6-tri-tert-butylphenoxide wasremoved from the sample immediately after charge and it was subject toelectron spin resonance spectroscopy as described in Example 1 to give aspin concentration of 10²¹ spin/g or more. It indicates that aftercharge, lithium 2,4,6-tri-tert-butylphenoxide was converted to2,4,6-tri-tert-butylphenoxyl radical.

Voltage variation in association with charge/discharge was evaluated asdescribed in Example 1. The results obtained indicated that the batterycould be repeatedly charged/discharged and also acted as a secondarybattery.

Example 5

On an aluminum foil was formed a compound layer containing lithium2,4,6-tri-tert-butylphenoxide as described in Example 4. A part of thelayer was removed and subject to electron spin resonance spectroscopy asdescribed in Example 1 to give a spin concentration of 10¹⁹ spin/g orless, indicating that a radical concentration is low in an initialstate.

Then, on a copper foil with a thickness of 20 μm was poured a slurryprepared by mixing polyvinylidene fluoride, N-methyl-2-pyrrolidone,powdered petroleum coke and acetylene black in a ratio of 1:30:20:1 byweight and the slurry was made even with a wire bar. After drying invacuo at 100° C. for 2 hours, the product was cut in a size of 1.5cm×1.5 cm to provide an electrode layer containing powdered petroleumcoke.

On the aluminum foil having the compound layer containing lithium2,4,6-tri-tert-butylphenoxide were sequentially laminated the gelelectrolyte film in Example 4 and the electrode layer containingpowdered petroleum coke. Then, the whole product was sandwiched withpolytetrafluoroethylene sheets and pressed to prepare a secondarybattery as described in Example 1.

For the secondary battery thus prepared, discharge with a constantcurrent of 0.1 mA was conducted using the copper foil with a compoundlayer containing lithium 2,4,6-tri-tert-butylphenoxide as a positiveelectrode and the copper comprising a layer of powdered petroleum cokeas a negative electrode. When the battery voltage became 3.0 V, thevoltage was kept constant. Then charge was terminated when a currentvalue became 0.01 mA. After a 5 min interval, discharge was started toobtain a discharge curve. In the curve, a plateau can be found at about2.0 V, indicating that the battery acted as a secondary battery. A partof the compound layer containing lithium 2,4,6-tri-tert-butylphenoxidewas removed from the sample immediately after charge and it was subjectto electron spin resonance spectroscopy as described in Example 1 togive a spin concentration of 10²¹ spin/g or more. It indicates thatafter charge, lithium 2,4,6-tri-tert-butylphenoxide was converted to2,4,6-tri-tert-butylphenoxyl radical. Voltage variation in associationwith charge/discharge was evaluated as described in Example 1. Theresults obtained indicated that the battery could be repeatedlycharged/discharged and also acted as a secondary battery.

Example 6

In a glass vessel in a dry box equipped with a gas purifier weresequentially placed 50 mg of 2,2,6,6-tetramethylpiperidinoxyl radical(TEMPOα radical) having the molecular structure represented by chemicalformula (A26) and 60 mg of graphite powder as a conductive adjuvantunder an atmosphere of argon. To the mixture were added 20 mg of acopolymer of vinylidene fluoride and hexafluoropropylene and 1 g oftetrahydrofuran, and the mixture was stirred for several minutes untilit became homogeneous to provide a black slurry. A sample of TEMPOαradical used was subject to electron spin resonance spectroscopy asdescribed in Example 1 to give a spin concentration of 10²¹ spin/g ormore.

Then, 200 mg of the slurry thus obtained was added dropwise on thesurface of an aluminum foil (area: 1.5 cm×1.5 cm, thickness: 100 μm)with a lead, and the slurry was spread using a wire bar such that theoverall surface became even. It was left for 60 mm at room temperatureto evaporate the solvent, tetrahydrofuran, and to form a layercontaining TEMPOα radical on the aluminum foil.

To 600 mg of a copolymer of vinylidene fluoride and hexafluoropropylenewere added 1400 mg of the 1:1 mixture of ethylene carbonate/propylenecarbonate containing 1 mol/L of LiPF₆ as an electrolyte salt and then11.3 g of tetrahydrofuran, and the mixture was stirred at roomtemperature. After dissolving the copolymer of vinylidene fluoride andhexafluoropropylene, the mixture was applied on a stepped glass plate.It was left for 1 hour for spontaneous evaporation of tetrahydrofuran toprovide a cast film with a thickness of 1 mm.

The gel electrolyte film cut by 2.0 cm×2.0 cm was laminated on thealuminum foil prepared above on which an electrode layer containingTEMPOα radical had been formed. On the foil was then laminated a copperfoil having a lithium film with a lead (thickness: 30 μm for the lithiumfilm and 20 μm for the copper foil). The whole product was sandwichedwith polytetrafluoroethylene sheets with a thickness of 5 mm and waspressed to provide a secondary battery.

For a sample of the secondary battery thus prepared, discharge with aconstant current of 0.1 mA was conducted using the electrode layercontaining TEMPOα radical as a positive electrode and the copper foilwith a lithium film as a negative electrode, indicating its action as asecondary battery. Repeated charge/discharge for the secondary batteryindicated that the battery acted as a secondary battery capable ofcharge/discharge for 10 cycles or more.

Example 7

In a glass vessel in a dry box equipped with a gas purifier weresequentially placed 50 mg of dibutylnitroxyl radical (DBNO radical)having the molecular structure represented by chemical formula (A12) and60 mg of graphite powder as a conductive adjuvant under an atmosphere ofargon. To the mixture were added 20 mg of a copolymer of vinylidenefluoride and hexafluoropropylene and 1 g of tetrahydrofuran, and themixture was stirred for several minutes until it became homogeneous toprovide a black slurry. A sample of DBNO radical used was subject toelectron spin resonance spectroscopy as described in Example 1 to give aspin concentration of 10²¹ spin/g or more.

Then, 200 mg of the slurry thus obtained was added dropwise on thesurface of an aluminum foil (area: 1.5 cm×1.5 cm, thickness: 100 μm)with a lead, and the slurry was spread using a wire bar such that theoverall surface became even. It was left for 60 min at room temperatureto evaporate the solvent, tetrahydrofuran, and to form a layercontaining DBNO radical on the aluminum foil.

To 600 mg of a copolymer of vinylidene fluoride and hexafluoropropylenewere added 1400 mg of the 1:1 mixture of ethylene carbonate/propylenecarbonate containing 1 mol/L of LiPF₆ as an electrolyte salt and then11.3 g of tetrahydrofuran, and the mixture was stirred at roomtemperature. After dissolving the copolymer of vinylidene fluoride andhexafluoropropylene, the mixture was applied on a stepped glass plate.It was left for 1 hour for spontaneous evaporation of tetrahydrofuran toprovide a cast film with a thickness of 1 mm.

The gel electrolyte film cut by 2.0 cm×2.0 cm was laminated on thealuminum foil prepared above on which an electrode layer containing DBNOradical had been formed. On the foil was then laminated a copper foilhaving a lithium film with a lead (thickness: 30 μm for the lithium filmand 20 μm for the copper foil). The whole product was sandwiched withpolytetrafluoroethylene sheets with a thickness of 5 mm and was pressedto provide a secondary battery.

For a sample of the secondary battery thus prepared, discharge with aconstant current of 0.1 mA was conducted using the electrode layercontaining DBNO radical as a positive electrode and the copper foil witha lithium film as a negative electrode, indicating its action as asecondary battery. Repeated charge/discharge for the secondary batteryindicated that the battery acted as a secondary battery capable ofcharge/discharge for 10 cycles or more.

Example 8

In a glass vessel in a dry box equipped with a gas purifier weresequentially placed 50 mg of diphenylnitroxyl radical (DPNO radical)having the molecular structure represented by chemical formula (A21) and60 mg of graphite powder as a conductive adjuvant under an atmosphere ofargon. To the mixture were added 20 mg of a copolymer of vinylidenefluoride and hexafluoropropylene and 1 g of tetrahydrofuran, and themixture was stirred for several minutes until it became homogeneous toprovide a black slurry. A sample of DPNO radical used was subject toelectron spin resonance spectroscopy as described in Example 1 to give aspin concentration of 10²¹ spin/g or more.

Then, 200 mg of the slurry thus obtained was added dropwise on thesurface of an aluminum foil (area: 1.5 cm×1.5 cm, thickness: 100 μm)with a lead, and the slurry was spread using a wire bar such that theoverall surface became even. It was left for 60 min at room temperatureto evaporate the solvent, tetrahydrofuran, and to form a layercontaining DPNO radical on the aluminum foil.

To 600 mg of a copolymer of vinylidene fluoride and hexafluoropropylenewere added 1400 mg of the 1:1 mixture of ethylene carbonate/propylenecarbonate containing 1 mol/L of LiPF₆ as an electrolyte salt and then11.3 g of tetrahydrofuran, and the mixture was stirred at roomtemperature. After dissolving the copolymer of vinylidene fluoride andhexafluoropropylene, the mixture was applied on a stepped glass plate.It was left for 1 hour for spontaneous evaporation of tetrahydrofuran toprovide a cast film with a thickness of 1 mm.

The gel electrolyte film cut by 2.0 cm×2.0 cm was laminated on thealuminum foil prepared above on which an electrode layer containing DPNOradical had been formed. On the foil was then laminated a copper foilhaving a lithium film with a lead (thickness: 30 μm for the lithium filmand 20 μm for the copper foil). The whole product was sandwiched withpolytetrafluoroethylene sheets with a thickness of 5 mm and was pressedto provide a secondary battery.

For a sample of the secondary battery thus prepared, discharge with aconstant current of 0.1 mA was conducted using the electrode layercontaining DPNO radical as a positive electrode and the copper foil witha lithium film as a negative electrode, indicating its action as asecondary battery. Repeated charge/discharge for the secondary batteryindicated that the battery acted as a secondary battery capable ofcharge/discharge for 10 cycles or more.

Example 9

In a glass vessel in a dry box equipped with a gas purifier weresequentially placed 50 mg of 3-amino-2,2,6,6-tetramethylpyrrolidinoxylradical (TEMPOs radical) having the molecular structure represented bychemical formula (A33) and 60 mg of graphite powder as a conductiveadjuvant under an atmosphere of argon. To the mixture were added 20 mgof a copolymer of vinylidene fluoride and hexafluoropropylene and 1 g oftetrahydrofuran, and the mixture was stirred for several minutes untilit became homogeneous to provide a black slurry. A sample of the radicalused was subject to electron spin resonance spectroscopy as described inExample 1 to give a spin concentration of 10²¹ spin/g or more.

Then, 200 mg of the slurry thus obtained was added dropwise on thesurface of an aluminum foil (area: 1.5 cm×1.5 cm, thickness: 100 μm)with a lead, and the slurry was spread using a wire bar such that theoverall surface became even. It was left for 60 min at room temperatureto evaporate the solvent, tetrahydrofuran, and to form a layercontaining TEMPOβ radical on the aluminum foil.

To 600 mg of a copolymer of vinylidene fluoride and hexafluoropropylenewere added 1400 mg of the 1:1 mixture of ethylene carbonate/propylenecarbonate containing 1 mol/L of LiPF₆ as an electrolyte salt and then11.3 g of tetrahydrofuran, and the mixture was stirred at roomtemperature. After dissolving the copolymer of vinylidene fluoride andhexafluoropropylene, the mixture was applied on a stepped glass plate.It was left for 1 hour for spontaneous evaporation of tetrahydrofuran toprovide a cast film with a thickness of 1 mm.

The gel electrolyte film cut by 2.0 cm×2.0 cm was laminated on thealuminum foil prepared above on which an electrode layer containingTEMPOβ radical had been formed. On the foil was then laminated a copperfoil having a lithium film with a lead (thickness: 30 μm for the lithiumfilm and 20 μm for the copper foil). The whole product was sandwichedwith polytetrafluoroethylene sheets with a thickness of 5 mm and waspressed to provide a secondary battery.

For a sample of the secondary battery thus prepared, discharge with aconstant current of 0.1 mA was conducted using the electrode layercontaining TEMPOβ radical as a positive electrode and the copper foilwith a lithium film as a negative electrode, indicating its action as asecondary battery. Repeated charge/discharge for the secondary batteryindicated that the battery acted as a secondary battery capable ofcharge/discharge for 10 cycles or more.

Example 10

In a glass vessel in a dry box equipped with a gas purifier weresequentially placed 50 mg of 3-amino-2,2,6,6-tetramethylpyrrolinoxylradical (TEMPOγ radical) having the molecular structure represented bychemical formula (A39) and 60 mg of graphite powder as a conductiveadjuvant under an atmosphere of argon. To the mixture were added 20 mgof a copolymer of vinylidene fluoride and hexafluoropropylene and 1 g oftetrahydrofuran, and the mixture was stirred for several minutes untilit became homogeneous to provide a black slurry. A sample of TEMPOγradical used was subject to electron spin resonance spectroscopy asdescribed in Example 1 to give a spin concentration of 10²¹ spin/g ormore.

Then, 200 mg of the slurry thus obtained was added dropwise on thesurface of an aluminum foil (area: 1.5 cm×1.5 cm, thickness: 100 μm)with a lead, and the slurry was spread using a wire bar such that theoverall surface became even. It was left for 60 min at room temperatureto evaporate the solvent, tetrahydrofuran, and to form a layercontaining TEMPOγ radical on the aluminum foil.

To 600 mg of a copolymer of vinylidene fluoride and hexafluoropropylenewere added 1400 mg of the 1:1 mixture of ethylene carbonate/propylenecarbonate containing 1 mol/L of LiPF₆ as an electrolyte salt and then11.3 g of tetrahydrofuran, and the mixture was stirred at roomtemperature. After dissolving the copolymer of vinylidene fluoride andhexafluoropropylene, the mixture was applied on a stepped glass plate.It was left for 1 hour for spontaneous evaporation of tetrahydrofuran toprovide a cast film with a thickness of 1 mm.

The gel electrolyte film cut by 2.0 cm×2.0 cm was laminated on thealuminum foil prepared above on which an electrode layer containingTEMPOγ radical had been formed. On the foil was then laminated a copperfoil having a lithium film with a lead (thickness: 30 μm for the lithiumfilm and 20 μm for the copper foil). The whole product was sandwichedwith polytetrafluoroethylene sheets with a thickness of 5 mm and waspressed to provide a secondary battery.

For a sample of the secondary battery thus prepared, discharge with aconstant current of 0.1 mA was conducted using the electrode layercontaining TEMPOγ radical as a positive electrode and the copper foilwith a lithium film as a negative electrode, indicating its action as asecondary battery. Repeated charge/discharge for the secondary batteryindicated that the battery acted as a secondary battery capable ofcharge/discharge for 10 cycles or more.

Example 11

In a glass vessel in a dry box equipped with a gas purifier weresequentially placed 50 mg of nitronylnitroxide compound (NONO) havingthe molecular structure represented by chemical formula (A43) and 60 mgof graphite powder as a conductive adjuvant under an atmosphere ofargon. To the mixture were added 20 mg of a copolymer of vinylidenefluoride and hexafluoropropylene and 1 g of tetrahydrofuran, and themixture was stirred for several minutes until it became homogeneous toprovide a black slurry. A sample of NONO used was subject to electronspin resonance spectroscopy as described in Example 1 to give a spinconcentration of 10²¹ spin/g or more.

Then, 200 mg of the slurry thus obtained was added dropwise on thesurface of an aluminum foil (area: 1.5 cm×1.5 cm, thickness: 100 μm)with a lead, and the slurry was spread using a wire bar such that theoverall surface became even. It was left for 60 min at room temperatureto evaporate the solvent, tetrahydrofuran, and to form a layercontaining NONO on the aluminum foil.

To 600 mg of a copolymer of vinylidene fluoride and hexafluoropropylenewere added 1400 mg of the 1:1 mixture of ethylene carbonate/propylenecarbonate containing 1 mol/L of LiPF₆ as an electrolyte salt and then11.3 g of tetrahydrofuran, and the mixture was stirred at roomtemperature. After dissolving the copolymer of vinylidene fluoride andhexafluoropropylene, the mixture was applied on a stepped glass plate.It was left for 1 hour for spontaneous evaporation of tetrahydrofuran toprovide a cast film with a thickness of 1 mm.

The gel electrolyte film cut by 2.0 cm×2.0 cm was laminated on thealuminum foil prepared above on which an electrode layer containing NONOhad been formed. On the foil was then laminated a copper foil having alithium film with a lead (thickness: 30 μm for the lithium film and 20μm for the copper foil). The whole product was sandwiched withpolytetrafluoroethylene sheets with a thickness of 5 mm and was pressedto provide a secondary battery.

For a sample of the secondary battery thus prepared, discharge with aconstant current of 0.1 mA was conducted using the electrode layercontaining NONO as a positive electrode and the copper foil with alithium film as a negative electrode, indicating its action as asecondary battery. Repeated charge/discharge for the secondary batteryindicated that the battery acted as a secondary battery capable ofcharge/discharge for 10 cycles or more.

Example 12

In a glass vessel in a dry box equipped with a gas purifier weresequentially placed 50 mg of galvinoxyl having the molecular structurerepresented by chemical formula B5 and 60 mg of graphite powder as aconductive adjuvant under an atmosphere of argon. To the mixture wereadded 20 mg of a copolymer of vinylidene fluoride andhexafluoropropylene and 1 g of tetrahydrofuran, and the mixture wasstirred for several minutes until it became homogeneous to provide ablack slurry. A sample of galvinoxyl used was subject to electron spinresonance spectroscopy as described in Example 1 to give a spinconcentration of 10²¹ spin/g or more, which indicated that the samplehas the structure having an oxy radical represented by chemical formula5 in an initial state.

Then, 200 mg of the slurry thus obtained was added dropwise on thesurface of an aluminum foil (area: 1.5 cm×1.5 cm, thickness: 100 μm)with a lead, and the slurry was spread using a wire bar such that theoverall surface became even. It was left for 60 min at room temperatureto evaporate the solvent, tetrahydrofuran, and to form a layercontaining galvinoxyl on the aluminum foil.

To 600 mg of a copolymer of vinylidene fluoride and hexafluoropropylenewere added 1400 mg of the 1:1 mixture of ethylene carbonate/propylenecarbonate containing 1 mol/L of LiPF₆ as an electrolyte salt and then11.3 g of tetrahydrofuran, and the mixture was stirred at roomtemperature. After dissolving the copolymer of vinylidene fluoride andhexafluoropropylene, the mixture was applied on a stepped glass plate.It was left for 1 hour for spontaneous evaporation of tetrahydrofuran toprovide a cast film with a thickness of 1 mm.

The gel electrolyte film cut by 2.0 cm×2.0 cm was laminated on thealuminum foil prepared above on which an electrode layer containinggalvinoxyl radical had been formed. On the foil was then laminated acopper foil having a lithium film with a lead (thickness: 30 μm for thelithium film and 20 μm for the copper foil). The whole product wassandwiched with polytetrafluoroethylene sheets with a thickness of 5 mmand was pressed to provide a secondary battery.

For a sample of the secondary battery thus prepared, discharge with aconstant current of 0.1 mA was conducted using the electrode layercontaining galvinoxyl radical as a positive electrode and the copperfoil with a lithium film as a negative electrode. The results showed avoltage plateau at about 2.3 V, indicating its action as a secondarybattery. Repeated charge/discharge for the secondary battery indicatedthat the battery acted as a secondary battery capable ofcharge/discharge for 10 cycles or more. A part of the positive electrodelayer was removed from the sample after discharge and was subject toelectron spin resonance spectroscopy to give a spin concentration of10¹⁹ spin/g or less. It suggested that after discharge, galvinoxylradical was consumed due to its formation of a bond with lithium ion.

Example 13

Fifty milligrams of poly(vinyl-di-tert-butylphenol) was treated withequimolar potassium ferricyanide and sodium hydroxide to providepoly(vinyl-di-tert-butylphenoxy radical). The product was subject toelectron spin resonance spectroscopy as described in Example 1 to give aspin concentration of 10²¹ spin/g or more. The results indicated thatthe product has the structure having an oxy radical represented bychemical formula B10 in an initial state.

A conductive adjuvant, a copolymer of vinylidenefluoride-hexafluoroethylene and tetrahydrofuran were mixed as describedin Example 12, substituting poly(vinyl-di-tert-butylphenoxy radical) forgalvinoxyl to provide a black slurry. Then, on an aluminum foil wasformed a compound layer containing poly(vinyl-di-tert-butylphenoxyradical) as described in Example 12.

On the aluminum foil comprising poly(vinyl-di-tert-butylphenoxy radical)was laminated a cast film cut by 2.0 cm×2.0 cm prepared from a mixedsolution of ethylene carbonate and propylene carbonate containing 1mol/L of LiPF₆ as an electrolyte salt in Example 12 and a copolymerelectrolyte of vinylidene fluoride and hexafluoropropylene. On theproduct was then laminated lithium as described in Example 12 to providea secondary battery.

For a sample of the secondary battery thus prepared, discharge with aconstant current of 0.1 mA was conducted using the electrode layercontaining poly(vinyl-di-tert-butylphenoxy radical) as a positiveelectrode and the copper foil with a lithium film as a negativeelectrode. The results showed a voltage plateau at about 2.4 V,indicating its action as a secondary battery. Voltage variation withcharge/discharge of the secondary battery was measured. The resultsindicated that the battery acted as a secondary battery. A part of thepositive electrode layer was removed from the sample after discharge andwas subject to electron spin resonance spectroscopy to give a spinconcentration of 10¹⁹ spin/g or less. It suggested that after discharge,poly(vinyl-di-tert-butylphenoxy radical) in the positive electrode wasconsumed due to, for example, its formation of a bond with lithium ion.

Example 14

Acetyl-di-tert-butylphenol was reacted with molybdenum pentachloride inbenzene at 40° C. to preparepoly(3,5-di-tert-butyl-4-hydroxyphenylacetylene). It was treated withpotassium ferricyanide and sodium hydroxide as described in Example 13to provide poly(acetyl-di-tert-butylphenoxy radical). The product wassubject to electron spin resonance spectroscopy as described in Example1 to give a spin concentration of 10²¹ spin/g or more. The resultsindicated that the product has the structure having an oxy radicalrepresented by chemical formula B12 in an initial state.

A conductive adjuvant, a copolymer of vinylidenefluoride-hexafluoroethylene and tetrahydrofuran were mixed as describedin Example 12, substituting poly(acetyl-di-tert-butylphenoxy radical)for galvinoxyl to provide a black slurry. Then, on an aluminum foil wasformed a compound layer containing poly(acetyl-di-tert-butylphenoxyradical) as described in Example 12.

On the aluminum foil comprising poly(acetyl-di-tert-butylphenoxyradical) was laminated a cast film cut by 2.0 cm×2.0 cm prepared from amixed solution of ethylene carbonate and propylene carbonate containing1 mol/L of LiPF₆ as an electrolyte salt in Example 12 and a copolymerelectrolyte of vinylidene fluoride and hexafluoropropylene. On theproduct was then laminated lithium as described in Example 12 to providea secondary battery.

For a sample of the secondary battery thus prepared, discharge with aconstant current of 0.1 mA was conducted using the electrode layercontaining poly(acetyl-di-tert-butylphenoxy radical) as a positiveelectrode and the copper foil with a lithium film as a negativeelectrode. The results showed a voltage plateau at about 3.3 V,indicating its action as a secondary battery. Voltage variation withcharge/discharge of the secondary battery was measured. The resultsindicated that the battery acted as a secondary battery. A part of thepositive electrode layer was removed from the sample after discharge andwas subject to electron spin resonance spectroscopy as described inExample 1 to give a spin concentration of 10¹⁹ spin/g or less. Itsuggested that after discharge, poly(acetyl-di-tert-butylphenoxyradical) in the positive electrode was consumed due to, for example, itsformation of a bond with lithium ion.

Example 15

In an electrolysis cell was placed a solution or dispersion of 0.25 M ofLiAsF₆, 0.25 M of CuCl₂ and 0.5 M of benzene in nitrobenzene. Twoplatinum plates were inserted into the solution/dispersion andelectrolysis was conducted at a voltage of 10 V to form a conductivepoly(paraphenylene) film with a film thickness of 10 μm on the surfaceof the positive electrode. At the end of the reaction, the electrodeswere short-circuited and the film was then removed from the electrode.The poly(paraphenylene) film was placed in a vacuum vessel, heated to450° C. with 0.1 mol of oxygen to its monomer unit and kept at thetemperature for 2 hours. The film was cooled to room temperature toobtain a sample. NMR and IR spectra for the sample suggested themolecular structure of the semiquinone represented by chemical formulaB9 in which a part of the poly(paraphenylene) was replaced with oxygen.ESR spectrum gave a spin concentration of 2×10²¹ spin/g for the sample.

The sample having the semiquinone structure was directly laminated on analuminum foil and the product was pressed. On the aluminum foil waslaminated a cast film cut by 2.0 cm×2.0 cm prepared from a mixedsolution of ethylene carbonate and propylene carbonate containing 1mol/L of LiPF₆ as an electrolyte salt in Example 12 and a copolymerelectrolyte of vinylidene fluoride and hexafluoropropylene. On theproduct was then laminated lithium as described in Example 12 to providea secondary battery.

For a sample of the secondary battery thus prepared, discharge with aconstant current of 0.1 mA was conducted using the electrode comprisingthe compound having the semiquinone structure as a positive electrodeand the copper foil with a lithium film as a negative electrode. Theresults showed a voltage plateau at about 3.1 V, indicating its actionas a secondary battery. Voltage variation with charge/discharge of thesecondary battery was measured. The results indicated that the batteryacted as a secondary battery. A part of the positive electrode layer wasremoved from the sample after discharge and was subject to electron spinresonance spectroscopy to give a spin concentration of 10¹⁹ spin/g orless. It suggested that after discharge, the compound having thesemiquinone structure in the positive electrode was consumed due to, forexample, its formation of a bond with lithium ion.

Example 16

In an electrolysis cell was placed powdered1,3,5-trisdiazo-cyclohexane-2,4,6-trione, which was then heated to 600°C. and kept at the temperature for 20 hours. The reaction was cooled toroom temperature to obtain a sample. NMR and IR spectra for the samplesuggested a network polyoxy radical whose molecular structure had thebasic structure represented by chemical formula B4. ESR spectrum gave aspin concentration of 8×10²¹ spin/g for the sample.

A conductive adjuvant, a copolymer of vinylidenefluoride-hexafluoroethylene and tetrahydrofuran were mixed as describedin Example 12, substituting the presumably network polyoxy radical forgalvinoxyl to provide a black slurry. Then, on an aluminum foil wasformed a compound layer containing the presumably network polyoxyradical as described in Example 12.

On the aluminum foil comprising the presumably network polyoxy radicalwas laminated a cast film cut by 2.0 cm×2.0 cm prepared from a mixedsolution of ethylene carbonate and propylene carbonate containing 1mol/L of LiPF₆ as an electrolyte salt in Example 12 and a copolymerelectrolyte of vinylidene fluoride and hexafluoropropylene. On theproduct was then laminated lithium as described in Example 12 to providea secondary battery.

For a sample of the secondary battery thus prepared, discharge with aconstant current of 0.1 mA was conducted using the electrode layercontaining the presumably network polyoxy radical as a positiveelectrode and the copper foil with a lithium film as a negativeelectrode. The results showed a voltage plateau at about 3.3 V,indicating its action as a secondary battery. Voltage variation withcharge/discharge of the secondary battery was measured. The resultsindicated that the battery acted as a secondary battery. A part of thepositive electrode layer was removed from the sample after discharge andwas subject to electron spin resonance spectroscopy as described inExample 1 to give a spin concentration of 10¹⁹ spin/g or less. Itsuggested that after discharge, the presumably network polyoxy radicalin the positive electrode was consumed due to, for example, itsformation of a bond with lithium ion.

Example 17

There will be described a process for preparing a secondary batteryusing diphenylpicrylhydrazyl represented by chemical formula (C29) as anactive material. In advance, diphenylpicrylhydrazyl was subject toelectron spin resonance spectroscopy to give a spin concentration of10²¹ spin/g or more.

In a dry box equipped with a gas purifier were mixed 60 mg of acopolymer of vinylidene fluoride and hexafluoropropylene and 140 mg ofan electrolyte solution which was a 1:1 mixture of ethylenecarbonate/propylene carbonate containing 1 mol/L of LiPF₆ electrolytesalt under an atmosphere of argon gas. To the mixture was added 1130 mgof tetrahydrofuran, and the mixture was dissolved to prepare a solutionof a gel electrolyte in tetrahydrofuran. In a separate glass vessel wasplaced 30 mg of diphenylpicrylhydrazyl, then 60 mg of graphite powder asa conductive adjuvant and then 200 mg of the above solution of a gelelectrolyte in tetrahydrofuran as an ion-conductive adjuvant, and themixture was blended. To the mixture was added 1000 mg of tetrahydrofuranand the mixture was further stirred for 3 hours to provide a blackslurry. Then, 200 mg of the slurry was added dropwise on the surface ofan aluminum foil (area: 1.5 cm×1.5 cm, thickness: 100 μm) with a lead,and the slurry was spread using a wire bar such that the overall surfacebecame even. It was left for 3 hours at room temperature tosubstantially evaporate the solvent, tetrahydrofuran, and to form anelectrode layer containing diphenylpicrylhydrazyl on the aluminum foil.

To 600 mg of a copolymer of vinylidene fluoride-hexafluoropropylene wereadded 1400 mg of an electrolyte solution, i.e., a 1:1 mixed solution ofethylene carbonate/propylene carbonate containing 1 mol/L of LiPF6 as anelectrolyte salt and 11.3 g of tetrahydrofuran, and the mixture wasstirred at room temperature. After dissolving the copolymer ofvinylidene fluoride-hexafluoropropylene, the solution was applied on aglass plate with a glass frame. The plate was dried in the air toevaporate tetrahydrofuran to provide a cast film with a thickness of 300μm on the glass plate.

The gel electrolyte film cut by 2.0 cm×2.0 cm was laminated on thealuminum foil on which diphenylpicrylhydrazyl had been formed. On thefoil was then laminated a copper foil having a lithium film with a lead(thickness: 30 μm for the lithium film and 20 μm for the copper foil).The whole product was sandwiched with polytetrafluoroethylene sheetswith a thickness of 5 mm and was pressed to provide a secondary battery.

For the secondary battery thus prepared, discharge with a constantcurrent of 0.1 mA was conducted using the electrode layer containingdiphenylpicrylhydrazyl as a positive electrode and the copper foil witha lithium film as a negative electrode. A voltage was constant at about2.5 V for about 5 hours and it took additional 12 hours for a voltage tobe reduced to 1 V or less. It was found that a voltage was kept constantat about 2.5 V after 10 cycles of charge/discharge, indicating that thebattery acted as a secondary battery. A part of the positive electrodelayer cut from the sample after discharge was subject to electron spinresonance spectroscopy to give a spin concentration of 10¹⁹ spin/g orless. It would be because diphenylpicrylhydrazyl was converted into acompound without a radical in an electrode reaction during discharge. Itwas thought that diphenylpicrylhydrazyl acted as an active material inthe positive electrode for action of the secondary battery.

Example 18

A secondary battery was prepared as described in Example 17,substituting triphenylpherdazyl having the molecular structurerepresented by chemical formula (C30) for diphenylpicrylhydrazyl, anddischarge was conducted. In advance, triphenylpherdazyl was subject toelectron spin resonance spectroscopy to give a spin concentration of10²¹ spin/g or more.

For the secondary battery thus prepared, discharge with a constantcurrent of 0.1 mA was conducted using the aluminum foil comprising acompound layer containing triphenylpherdazyl as a positive electrode andthe copper foil with a lithium film as a negative electrode. A plateauwas found at about 2.3 V and it took 8 hours for a voltage to be reducedto 1 V or less. A part of the positive electrode layer cut from thesample after discharge was subject to electron spin resonancespectroscopy to give a spin concentration of 10¹⁹ spin/g or less. Itwould be because triphenylpherdazyl was converted into a compoundwithout a radical in an electrode reaction during discharge. It wasthought that triphenylpherdazyl acted as an active material in thepositive electrode for action of the secondary battery.

Example 19

A secondary battery was prepared as described in Example 17,substituting a polymer compound having the pherdazyl structurerepresented by chemical formula (C31) for diphenylpicrylhydrazyl, anddischarge was conducted. In advance, the polymer compound having themolecular structure represented by chemical formula (C31) was subject toelectron spin resonance spectroscopy to give a spin concentration of10²¹ spin/g or more.

For the secondary battery thus prepared, discharge with a constantcurrent of 0.1 mA was conducted using the aluminum foil comprising thelayer of the polymer compound having the molecular structure representedby chemical formula (C31) and the copper foil with a lithium film as anegative electrode. A plateau was found at about 2.3 V and it took 12hours for a voltage to be reduced to 1 V or less.

Example 20

A secondary battery was prepared as described in Example 17,substituting a polymer compound having the aminotriazine structurerepresented by chemical formula (C32) for diphenylpicrylhydrazyl, anddischarge was conducted. In advance, the polymer compound having themolecular structure represented by chemical formula (C32) was subject toelectron spin resonance spectroscopy to give a spin concentration of10²¹ spin/g or more.

For the secondary battery thus prepared, discharge with a constantcurrent of 0.1 mA was conducted using the aluminum foil comprising thelayer of the polymer compound having the molecular structure representedby chemical formula (C32) and the copper foil with a lithium film as anegative electrode. A plateau was found at about 2.3 V and it took 10hours for a voltage to be reduced to 1 V or less.

Comparative Example 2

A secondary battery was prepared as described in Example 17, withoutusing a compound having a radical on a nitrogen atom as an activematerial, and discharge was conducted at a constant current of 0.1 mA. Avoltage was rapidly reduced to 0.8 V in about 50 min. In attemptingcharge by applying a constant current of 0.1 mA, a voltage wasmomentarily increased over 3.0 V and during re-discharge was rapidlyreduced to 0.8 V in about 50 min. It indicated that the battery did notact as a secondary battery.

Example 21

On the aluminum foil comprising an organic compound layer containingTEMPO radical prepared in Example 1 were laminated the gel electrolytefilm as described in Example 1 and then a copper foil having a lithiumfilm with a lead. The whole product was sandwiched withpolytetrafluoroethylene sheets with a thickness of 5 mm and was pressedto provide a secondary battery.

For the secondary battery thus prepared, charge with a constant currentof 0.1 mA was conducted using the aluminum foil comprising an organiccompound layer containing TEMPO radical as a positive electrode and thecopper foil with a lithium film as a negative electrode. A voltageplateau was found at about 3.5 V, indicating that the battery acted as asecondary battery. A part of the compound layer containing TEMPO radicalcut from the sample after discharge was subject to electron spinresonance spectroscopy as described in Example 1 to give a spinconcentration of 10¹⁹ spin/g or less. It may indicate that after charge,TEMPO radical formed a bond with an electrolyte anion to consumeradical. After discharging the secondary battery at a constant currentof 0.1 mA, it was subject to electron spin resonance spectroscopy togive a spin concentration of 10²¹ spin/g or more, suggesting that in thepositive electrode, discharge caused cleavage of the bond with theelectrolyte anion to form a radical compound.

A secondary battery was prepared as described above for measuringvoltage variation with charge/discharge. The battery exhibited a plateauin its discharge curve even after repeated charge/discharge; in otherwords, it also acted as a secondary battery.

As described above, a radical compound is used as a material involved inan electrode reaction according to this invention, so that there can beprovided a stable secondary battery with a higher energy density and alarger capacity.

This application is based on Japanese patent applications NO.2000-49705, NO. 2000-242806, NO. 2000-266922, NO. 2000-368475, thecontent of which is incorporated hereinto by reference.

1. An active material for a secondary battery comprising a radicalcompound having a nitroxyl radical of the formula (A1).


2. The active material for a secondary battery as claimed in claim 1wherein a spin concentration of the radical compound is 10²¹ spins/g ormore.
 3. The active material for a secondary battery as claimed in claim1 used in a positive electrode in the secondary battery.
 4. The activematerial for a secondary battery as claimed in claim 1 wherein theradical compound comprises a nitroxyl radical compound represented bygeneral formula (A2):

wherein X₁ and X₂ are a substituent containing at least one of analiphatic group, an aromatic group, hydroxy, alkoxy, aldehyde, carboxyl,alkoxycarbonyl, cyano, amino, nitro, nitroso, halogen or hydrogen,provided that when X₁ and X₂ contain an aliphatic group, the aliphaticgroup may be saturated or unsaturated, substituted or unsubstituted, andstraight, cyclic or branched, and may contain at least one of oxygen,nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms; when X₁and X₂ contain an aromatic group, the aromatic group may be substitutedor unsubstituted and may contain at least one of oxygen, nitrogen,sulfur, silicon, phosphorous, boron and halogen atoms; when X₁ and X₂contain hydroxy, the hydroxy may form a salt with a metal atom; when X₁and X₂ contain alkoxy, aldehyde, carboxyl, alkoxycarbonyl, cyano, amino,nitro or nitroso, these substituents may be substituted or unsubstitutedand may contain at least one of oxygen, nitrogen, sulfur, silicone,phosphorous, boron and halogen atoms; X₁ and X₂ may be the same ordifferent; and X₁ and X₂ taken together may form a ring.
 5. The activematerial for a secondary battery as claimed in claim 1 wherein theradical compound is a nitroxyl radical compound in which a nitrogen atomin the nitroxyl radical is bound to at least one alkyl, represented bygeneral formula (A3):

wherein R is alkyl which may be substituted or unsubstituted, straight,cyclic or branched, and may contain at least one of oxygen, nitrogen,sulfur, silicon, phosphorous, boron and halogen atoms; X is asubstituent containing at least one of an aliphatic group, an aromaticgroup, hydroxy, alkoxy, aldehyde, carboxyl, alkoxycarbonyl, cyano,amino, nitro, nitroso, halogen or hydrogen, provided that when Xcontains an aliphatic group, the aliphatic group may be saturated orunsaturated, substituted or unsubstituted, and straight, cyclic orbranched, and may contain at least one of oxygen, nitrogen, sulfur,silicon, phosphorous, boron and halogen atoms; when X contains anaromatic group, the aromatic group may be substituted or unsubstitutedand may contain at least one of oxygen, nitrogen, sulfur, silicon,phosphorous, boron and halogen atoms; when X contains hydroxy, thehydroxy may form a salt with a metal atom; when X contains alkoxy,aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro or nitroso, thesubstituent may be substituted or unsubstituted and may contain at leastone of oxygen, nitrogen, sulfur, silicon, phosphorous, boron and halogenatoms; and X may form a ring.
 6. The active material for a secondarybattery as claimed in claim 5 wherein the alkyl group is tert-butyl. 7.The active material for a secondary battery as claimed in claim 1wherein the radical compound is a nitroxyl radical compound in which anitrogen atom in the nitroxyl radical is bound to at least two alkyls,represented by general formula (A4):

wherein R₁ and R₂ are alkyl which may be substituted or unsubstituted,straight, cyclic or branched, and may contain at least one of oxygen,nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms; R₁ andR₂ may be the same or different; X₁ and X₂ are a substituent containingat least one of an aliphatic group, an aromatic group, hydroxy, alkoxy,aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro, nitroso,halogen or hydrogen, provided that when X₁ and X₂ contain an aliphaticgroup, the aliphatic group may be saturated or unsaturated, substitutedor unsubstituted, and straight, cyclic or branched, and may contain atleast one of oxygen, nitrogen, sulfur, silicon, phosphorous, boron andhalogen atoms; when X₁ and X₂ contain an aromatic group, the aromaticgroup may be substituted or unsubstituted and may contain at least oneof oxygen, nitrogen, sulfur, silicon, phosphorous, boron and halogenatoms; when X₁ and X₂ contain hydroxy, the hydroxy may form a salt witha metal atom; when X₁ and X₂ contain alkoxy, aldehyde, carboxyl,alkoxycarbonyl, cyano, amino, nitro or nitroso, these substituents maybe substituted or unsubstituted and may contain at least one of oxygen,nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms; X₁ andX₂ may be the same or different; and X₁ and X₂ may form a ring.
 8. Theactive material for a secondary battery as claimed in claim 7 whereinboth of the alkyls R₁ and R₂ are methyl.
 9. The active material for asecondary battery as claimed in claim 1 wherein the radical compound isa nitroxyl radical compound in which a nitrogen atom in the nitroxylradical is bound to two carbon atoms bound to at least two alkyls,represented by general formula (A5):

wherein R₁ to R₄ are alkyl which may be substituted or unsubstituted,straight, cyclic or branched, and may contain at least one of oxygen,nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms; R₁ toR₄ may be the same or different; X₁ and X₂ are a substituent containingat least one of an aliphatic group, an aromatic group, hydroxy, alkoxy,aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro, nitroso,halogen or hydrogen, provided that when X₁ and X₂ contain an aliphaticgroup, the aliphatic group may be saturated or unsaturated, substitutedor unsubstituted, and straight, cyclic or branched, and may contain atleast one of oxygen, nitrogen, sulfur, silicon, phosphorous, boron andhalogen atoms; when X₁ and X₂ contain an aromatic group, the aromaticgroup may be substituted or unsubstituted and may contain at least oneof oxygen, nitrogen, sulfur, silicon, phosphorous, boron and halogenatoms; when X₁ and X₂ contain hydroxy, the hydroxy may form a salt witha metal atom; when X₁ and X₂ contain alkoxy, aldehyde, carboxyl,alkoxycarbonyl, cyano, amino, nitro or nitroso, these substituents maybe substituted or unsubstituted and may contain at least one of oxygen,nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms; X₁ andX₂ may be the same or different; and X₁ and X₂ may form a ring.
 10. Theactive material for a secondary battery as claimed in claim 9 whereinall of the alkyls R₁ to R₄ are methyl.
 11. The active material for asecondary battery as claimed in claim 1 wherein the radical compound isa nitroxyl radical compound in which a nitrogen atom in the nitroxylradical is bound to at least one aryl, represented by general formula(A6):

wherein Ar is aryl which may be substituted or unsubstituted and maycontain at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,boron and halogen atoms; X is a substituent containing at least one ofan aliphatic group, an aromatic group, hydroxy, alkoxy, aldehyde,carboxyl, alkoxycarbonyl, cyano, amino, nitro, nitroso, halogen orhydrogen, provided that when X contains an aliphatic group, thealiphatic group may be saturated or unsaturated, substituted orunsubstituted, and straight, cyclic or branched, and may contain atleast one of oxygen, nitrogen, sulfur, silicon, phosphorous, boron andhalogen atoms; when X contains an aromatic group, the aromatic group maybe substituted or unsubstituted and may contain at least one of oxygen,nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms; when Xcontains hydroxy, the hydroxy may form a salt with a metal atom; when Xcontains alkoxy, aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitroor nitroso, the substituent may be substituted or unsubstituted and maycontain at least one of oxygen, nitrogen, sulfur, silicon, phosphorous,boron and halogen atoms; and X may form a ring.
 12. The active materialfor a secondary battery as claimed in claim 11 wherein the aryl issubstituted or unsubstituted phenyl.
 13. The active material for asecondary battery as claimed in claim 1 wherein the radical compoundforms a substituted or unsubstituted heterocycle represented by generalformula (A7):

wherein X is carbon, oxygen, nitrogen, sulfur, silicon, phosphorous orboron atom, provided that X may be the same or different; X may be boundvia saturated or unsaturated bonds; X may form a bond with anysubstituent; this compound may be a polymer which may be straight,cyclic or branched; and n is an integer of 2 to 10 both inclusive. 14.The active material for a secondary battery as claimed in claim 13wherein the radical compound has a piperidinoxyl ring structurerepresented by general formula (A8):

where R_(1 to R) ₄ are alkyl which may be substituted or unsubstituted,straight, cyclic or branched, and may contain at least one of oxygen,nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms; X is asubstituent containing at least one of an aliphatic group, an aromaticgroup, hydroxy, alkoxy, aldehyde, carboxyl, alkoxycarbonyl, cyano,amino, nitro, nitroso, halogen or hydrogen, provided that when Xcontains an aliphatic group, the aliphatic group may be saturated orunsaturated, substituted or unsubstituted, and straight, cyclic orbranched, and may contain at least one of oxygen, nitrogen, sulfur,silicon, phosphorous, boron and halogen atoms; when X contains anaromatic group, the aromatic group may be substituted or unsubstitutedand may contain at least one of oxygen, nitrogen, sulfur, silicon,phosphorous, boron and halogen atoms; when X contains hydroxy, thehydroxy may form a salt with a metal atom; when X contains alkoxy,aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro or nitroso, thesubstituent may be substituted or unsubstituted and may contain at leastone of oxygen, nitrogen, sulfur, silicon, phosphorous, boron and halogenatoms; and X may form a ring.
 15. The active material for a secondarybattery as claimed in claim 13 wherein the radical compound has apyrrolidinoxyl ring structure represented by general formula (A9):

where R₁ to R₄ are alkyl which may be substituted or unsubstituted,straight, cyclic or branched, and may contain at least one of oxygen,nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms; X is asubstituent containing at least one of an aliphatic group, an aromaticgroup, hydroxy, alkoxy, aldehyde, carboxyl, alkoxycarbonyl, cyano,amino, nitro, nitroso, halogen or hydrogen, provided that when Xcontains an aliphatic group, the aliphatic group may be saturated orunsaturated, substituted or unsubstituted, and straight, cyclic orbranched, and may contain at least one of oxygen, nitrogen, sulfur,silicon, phosphorous, boron and halogen atoms; when X contains anaromatic group, the aromatic group may be substituted or unsubstitutedand may contain at least one of oxygen, nitrogen, sulfur, silicon,phosphorous, boron and halogen atoms; when X contains hydroxy, thehydroxy may form a salt with a metal atom; when X contains alkoxy,aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro or nitroso, thesubstituent may be substituted or unsubstituted and may contain at leastone of oxygen, nitrogen, sulfur, silicon, phosphorous, boron and halogenatoms; and X may form a ring.
 16. The active material for a secondarybattery as claimed in claim 13 wherein the radical compound has apyrrolinoxyl ring structure represented by general formula (A10):

where R₁ to R₄ are alkyl which may be substituted or unsubstituted,straight, cyclic or branched, and may contain at least one of oxygen,nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms; X is asubstituent containing at least one of an aliphatic group, an aromaticgroup, hydroxy, alkoxy, aldehyde, carboxyl, alkoxycarbonyl, cyano,amino, nitro, nitroso, halogen or hydrogen, provided that when Xcontains an aliphatic group, the aliphatic group may be saturated orunsaturated, substituted or unsubstituted, and straight, cyclic orbranched, and may contain at least one of oxygen, nitrogen, sulfur,silicon, phosphorous, boron and halogen atoms; when X contains anaromatic group, the aromatic group may be substituted or unsubstitutedand may contain at least one of oxygen, nitrogen, sulfur, silicon,phosphorous, boron and halogen atoms; when X contains hydroxy, thehydroxy may form a salt with a metal atom; when X contains alkoxy,aldehyde, carboxyl, alkoxycarbonyl, cyano, amino, nitro or nitroso, thesubstituent may be substituted or unsubstituted and may contain at leastone of oxygen, nitrogen, sulfur, silicon, phosphorous, boron and halogenatoms; and X may form a ring.
 17. The active material for a secondarybattery as claimed in claim 1 wherein the radical compound is a compoundforming a nitronylnitroxide structure, represented by general formula(A11):

where X₁ to X₃ are a substituent containing at least one of an aliphaticgroup, an aromatic group, hydroxy, alkoxy, aldehyde, carboxyl,alkoxycarbonyl, cyano, amino, nitro, nitroso, halogen or hydrogen,provided that when X₁ to X₃ contain an aliphatic group, the aliphaticgroup may be saturated or unsaturated, substituted or unsubstituted, andstraight, cyclic or branched, and may contain at least one of oxygen,nitrogen, sulfur, silicon, phosphorous, boron and halogen atoms; when X₁to X₃ contain an aromatic group, the aromatic group may be substitutedor unsubstituted and may contain at least one of oxygen, nitrogen,sulfur, silicon, phosphorous, boron and halogen atoms; when X₁ to X₃contain hydroxy, the hydroxy may form a salt with a metal atom; when X₁to X₃ contain alkoxy, aldehyde, carboxyl, alkoxycarbonyl, cyano, amino,nitro or nitroso, these substituents may be substituted or unsubstitutedand may contain at least one of oxygen, nitrogen, sulfur, silicon,phosphorous, boron and halogen atoms; X₁ to X₃ may be the same ordifferent; and X₁ to X₃ may form a ring.
 18. The active material for asecondary battery as claimed in claim 1 wherein the radical compound isa polymer.
 19. The active material for a secondary battery as claimed inclaim 18 wherein the polymer has a polyacetylene main chain.
 20. Theactive material for a secondary battery as claimed in claim 18 whereinthe polymer has a polyphenylene-vinylene main chain.
 21. An activematerial for a secondary battery comprising a phenoxyl radical compound.22. The active material for a secondary battery as claimed in claim 21wherein the phenoxyl radical compound comprises a tert-butyl group. 23.The active material for a secondary battery as claimed in claim 21wherein the phenoxyl radical compound comprises a di-tert-butylphenoxyradical group.
 24. The active material for a secondary battery asclaimed in claim 21 wherein the phenoxyl radical compound is a polymer.25. The active material for a secondary battery as claimed in claim 24wherein the polymer has a polyolefin structure.
 26. The active materialfor a secondary battery as claimed in claim 24 wherein the polymer has apolyacetylene structure.
 27. The active material for a secondary batteryas claimed in claim 24 wherein the polymer has a polyphenylenestructure.
 28. The active material for a secondary battery as claimed inclaim 24 wherein the polymer has a five-membered aromatic heterocyclicstructure.
 29. The active material for a secondary battery as claimed inclaim 24 wherein the polymer has a three-dimensional network structure.30. An active material for a secondary battery comprising a radicalcompound having a triphenylpherdazyl group represented by chemicalformula (C3) or (C4)


31. An active material for a secondary battery comprising a radicalcompound having an aminotriazine structure represented by generalformula (C7):

where R₆ represents hydrogen, substituted or unsubstituted aliphatic oraromatic hydrocarbon, halogen, hydroxy, nitro, nitroso, cyano, alkoxy,aryloxy, alkoxycarbonyl, aryloxycarbonyl, acyl, carboxy or oxo radical.32. The active material for a secondary battery as claimed in claim 31wherein the radical compound is a polymer having the aminotriazinestructure represented by general formula (C7) as a repeating unit.